diff --git a/build-zip.php b/build-zip.php
index 331dee0..ec68df9 100644
--- a/build-zip.php
+++ b/build-zip.php
@@ -9,7 +9,7 @@
  * was produced ships to the client.
  *
  * Exclusion rule (keep in sync with the "no docs/AI files in zips" preference):
- *   - any path segment: .git, .claude, .github, docs, build, node_modules
+ *   - any path segment: .git, .claude, .github, docs, build, node_modules, tests
  *   - any *.md file
  *   - dotfiles at any level except .htaccess
  */
@@ -22,7 +22,7 @@ if ( '' === $src || '' === $out || ! is_dir( $src ) ) {
 	exit( 1 );
 }
 
-$excluded_dirs = array( '.git', '.claude', '.github', 'docs', 'build', 'node_modules' );
+$excluded_dirs = array( '.git', '.claude', '.github', 'docs', 'build', 'node_modules', 'tests' );
 
 function is_excluded( $rel, array $excluded_dirs ) {
 	$parts = explode( '/', $rel );
diff --git a/viator-collector/includes/class-vc-structure.php b/viator-collector/includes/class-vc-structure.php
new file mode 100644
index 0000000..fadf350
--- /dev/null
+++ b/viator-collector/includes/class-vc-structure.php
@@ -0,0 +1,208 @@
+<?php
+defined( 'ABSPATH' ) || exit;
+
+/**
+ * The client-managed region → city structure behind the /{region}/,
+ * /{city}/ and /{city}/{product}/ URLs.
+ *
+ * Everything here except get() is plain PHP so it can be unit-tested
+ * without WordPress (see tests/run.php).
+ *
+ * Shape: list of regions, each
+ *   array( 'name', 'slug', 'term_id', 'cities' => list of array( 'id', 'name', 'slug' ) )
+ * where a city's 'id' is its Viator destination id.
+ */
+class VC_Structure {
+	const OPTION = 'vc_structure';
+
+	private static $cache = null;
+
+	public static function default_regions() {
+		$regions = array(
+			'uk'                     => 'UK',
+			'europe'                 => 'Europe',
+			'asia'                   => 'Asia',
+			'middle-east-and-africa' => 'Middle East and Africa',
+			'americas'               => 'Americas',
+			'australasia'            => 'Australasia',
+		);
+		$out     = array();
+		foreach ( $regions as $slug => $name ) {
+			$out[] = array(
+				'name'    => $name,
+				'slug'    => $slug,
+				'term_id' => 0,
+				'cities'  => array(),
+			);
+		}
+		return $out;
+	}
+
+	public static function get() {
+		if ( null === self::$cache ) {
+			$value       = get_option( self::OPTION, self::default_regions() );
+			self::$cache = is_array( $value ) ? $value : self::default_regions();
+		}
+		return self::$cache;
+	}
+
+	/**
+	 * Drop the per-request cache (after the option is saved).
+	 */
+	public static function flush_cache() {
+		self::$cache = null;
+	}
+
+	public static function slugify( $s ) {
+		$s = strtolower( (string) $s );
+		$s = preg_replace( '/[^a-z0-9]+/', '-', $s );
+		return trim( $s, '-' );
+	}
+
+	/**
+	 * Shape submitted form data into the structure. Admin-typed slugs are only
+	 * trimmed/lowercased here — validate() rejects anything still invalid
+	 * rather than silently rewriting it.
+	 */
+	public static function normalize( array $raw ) {
+		$out = array();
+		foreach ( $raw as $region ) {
+			if ( ! is_array( $region ) ) {
+				continue;
+			}
+			$name   = trim( (string) ( $region['name'] ?? '' ) );
+			$slug   = strtolower( trim( (string) ( $region['slug'] ?? '' ) ) );
+			$cities = array();
+			foreach ( (array) ( $region['cities'] ?? array() ) as $city ) {
+				$id = trim( (string) ( is_array( $city ) ? ( $city['id'] ?? '' ) : '' ) );
+				if ( '' === $id ) {
+					continue;
+				}
+				$city_name = trim( (string) ( $city['name'] ?? '' ) );
+				$city_slug = strtolower( trim( (string) ( $city['slug'] ?? '' ) ) );
+				$cities[]  = array(
+					'id'   => $id,
+					'name' => $city_name,
+					'slug' => '' !== $city_slug ? $city_slug : self::slugify( $city_name ),
+				);
+			}
+			$out[] = array(
+				'name'    => $name,
+				'slug'    => '' !== $slug ? $slug : self::slugify( $name ),
+				'term_id' => (int) ( $region['term_id'] ?? 0 ),
+				'cities'  => $cities,
+			);
+		}
+		return $out;
+	}
+
+	public static function reserved_slugs() {
+		return array( 'wp-admin', 'wp-content', 'wp-includes', 'wp-json', 'feed', 'page', 'search', 'tag', 'category', 'author', 'tours', 'tour-destination', 'tour-tag', 'tour-category', 'blog', 'about', 'contact', 'faq', 'embed', 'attachment' );
+	}
+
+	/**
+	 * @param array $destination_map Viator destination id => name.
+	 * @param array $taken           slug => label, for slugs owned outside the structure.
+	 * @return string[] Errors; empty when valid.
+	 */
+	public static function validate( array $structure, array $destination_map, array $taken ) {
+		$errors   = array();
+		$slugs    = array();
+		$city_ids = array();
+
+		foreach ( $structure as $i => $region ) {
+			if ( '' === trim( (string) $region['name'] ) ) {
+				$errors[] = sprintf( 'Region %d has no name.', $i + 1 );
+			}
+			$slugs[] = (string) $region['slug'];
+
+			foreach ( $region['cities'] as $city ) {
+				$id = (string) $city['id'];
+				if ( ! isset( $destination_map[ $id ] ) ) {
+					$errors[] = sprintf( 'City ID %s is not a Viator destination.', $id );
+				}
+				if ( isset( $city_ids[ $id ] ) ) {
+					$errors[] = sprintf( '%s is listed more than once.', '' !== $city['name'] ? $city['name'] : $id );
+				}
+				$city_ids[ $id ] = true;
+				$slugs[]         = (string) $city['slug'];
+			}
+		}
+
+		$reserved = self::reserved_slugs();
+		foreach ( array_count_values( $slugs ) as $slug => $count ) {
+			$slug = (string) $slug;
+			if ( ! preg_match( '/^[a-z0-9]+(?:-[a-z0-9]+)*$/', $slug ) ) {
+				$errors[] = sprintf( 'Slug "%s" is invalid: use only a-z, 0-9 and -.', $slug );
+				continue;
+			}
+			if ( in_array( $slug, $reserved, true ) ) {
+				$errors[] = sprintf( 'Slug "%s" is reserved.', $slug );
+			}
+			if ( $count > 1 ) {
+				$errors[] = sprintf( 'Slug "%s" is used more than once.', $slug );
+			}
+			if ( isset( $taken[ $slug ] ) ) {
+				$errors[] = sprintf( 'Slug "%s" is already used by %s.', $slug, $taken[ $slug ] );
+			}
+		}
+
+		return array_values( array_unique( $errors ) );
+	}
+
+	/**
+	 * Configured cities in settings order: viator id => city + 'region' slug.
+	 */
+	public static function cities( array $structure ) {
+		$out = array();
+		foreach ( $structure as $region ) {
+			foreach ( $region['cities'] as $city ) {
+				$out[ (string) $city['id'] ] = $city + array( 'region' => $region['slug'] );
+			}
+		}
+		return $out;
+	}
+
+	/**
+	 * The city a product's URL lives under: its Viator primary destination
+	 * when configured, else the first configured city it belongs to, else ''.
+	 */
+	public static function canonical_city( array $structure, array $dest_ids, $primary_id ) {
+		$cities = self::cities( $structure );
+		if ( '' !== (string) $primary_id && isset( $cities[ (string) $primary_id ] ) ) {
+			return $cities[ (string) $primary_id ]['slug'];
+		}
+		$dest_ids = array_map( 'strval', $dest_ids );
+		foreach ( $cities as $id => $city ) {
+			if ( in_array( (string) $id, $dest_ids, true ) ) {
+				return $city['slug'];
+			}
+		}
+		return '';
+	}
+
+	public static function primary_destination_id( array $destinations ) {
+		foreach ( $destinations as $destination ) {
+			if ( is_array( $destination ) && ! empty( $destination['primary'] ) ) {
+				$ref = $destination['ref'] ?? ( $destination['destinationId'] ?? '' );
+				return (string) $ref;
+			}
+		}
+		return '';
+	}
+
+	/**
+	 * Explicit per-slug rules (no catch-alls), regions first, then cities.
+	 */
+	public static function rewrite_rules( array $structure ) {
+		$rules = array();
+		foreach ( $structure as $region ) {
+			$rules[ '^' . $region['slug'] . '/?$' ] = 'index.php?viator_destination=' . $region['slug'];
+		}
+		foreach ( self::cities( $structure ) as $city ) {
+			$rules[ '^' . $city['slug'] . '/?$' ]         = 'index.php?viator_destination=' . $city['slug'];
+			$rules[ '^' . $city['slug'] . '/([^/]+)/?$' ] = 'index.php?viator_tour=$matches[1]';
+		}
+		return $rules;
+	}
+}
diff --git a/viator-collector/tests/run.php b/viator-collector/tests/run.php
new file mode 100644
index 0000000..2f4d23a
--- /dev/null
+++ b/viator-collector/tests/run.php
@@ -0,0 +1,44 @@
+<?php
+/**
+ * Minimal test runner for the WordPress-free parts of the plugin.
+ *
+ *   php tests/run.php
+ */
+
+define( 'ABSPATH', __DIR__ . '/' );
+
+require_once dirname( __DIR__ ) . '/includes/class-vc-structure.php';
+
+function vc_assert_same( $expected, $actual, $msg = '' ) {
+	if ( $expected !== $actual ) {
+		throw new Exception( $msg . "\n  expected: " . var_export( $expected, true ) . "\n  actual:   " . var_export( $actual, true ) );
+	}
+}
+
+function vc_assert_contains( $needle, array $errors ) {
+	if ( ! in_array( $needle, $errors, true ) ) {
+		throw new Exception( 'Missing error: ' . $needle . "\n  got: " . var_export( $errors, true ) );
+	}
+}
+
+foreach ( glob( __DIR__ . '/test-*.php' ) as $file ) {
+	require_once $file;
+}
+
+$passed = 0;
+$failed = 0;
+foreach ( get_defined_functions()['user'] as $fn ) {
+	if ( 0 !== strpos( $fn, 'test_' ) ) {
+		continue;
+	}
+	try {
+		$fn();
+		$passed++;
+	} catch ( Throwable $e ) {
+		$failed++;
+		echo 'FAIL ' . $fn . ': ' . $e->getMessage() . "\n";
+	}
+}
+
+echo $passed . ' passed, ' . $failed . " failed\n";
+exit( $failed ? 1 : 0 );
diff --git a/viator-collector/tests/test-structure.php b/viator-collector/tests/test-structure.php
new file mode 100644
index 0000000..3acdc9f
--- /dev/null
+++ b/viator-collector/tests/test-structure.php
@@ -0,0 +1,149 @@
+<?php
+/**
+ * VC_Structure unit tests.
+ */
+
+function vc_fixture_structure() {
+	return array(
+		array(
+			'name'    => 'Europe',
+			'slug'    => 'europe',
+			'term_id' => 0,
+			'cities'  => array(
+				array( 'id' => '737', 'name' => 'Amsterdam', 'slug' => 'amsterdam' ),
+				array( 'id' => '479', 'name' => 'Paris', 'slug' => 'paris' ),
+			),
+		),
+		array(
+			'name'    => 'Americas',
+			'slug'    => 'americas',
+			'term_id' => 0,
+			'cities'  => array(
+				array( 'id' => '678', 'name' => 'Boston', 'slug' => 'boston' ),
+			),
+		),
+	);
+}
+
+function vc_fixture_map() {
+	return array( '737' => 'Amsterdam', '479' => 'Paris', '678' => 'Boston', '22' => 'Victoria' );
+}
+
+function test_default_regions() {
+	$regions = VC_Structure::default_regions();
+	vc_assert_same(
+		array( 'uk', 'europe', 'asia', 'middle-east-and-africa', 'americas', 'australasia' ),
+		array_column( $regions, 'slug' )
+	);
+	vc_assert_same( 'Middle East and Africa', $regions[3]['name'] );
+	vc_assert_same( array(), $regions[0]['cities'] );
+	vc_assert_same( 0, $regions[0]['term_id'] );
+}
+
+function test_normalize_fills_slugs() {
+	$s = VC_Structure::normalize(
+		array(
+			array(
+				'name'    => ' Middle East and Africa ',
+				'slug'    => '',
+				'term_id' => '7',
+				'cities'  => array(
+					array( 'id' => '', 'name' => 'Ghost', 'slug' => 'ghost' ),
+					array( 'id' => '828', 'name' => 'Dubai', 'slug' => '' ),
+				),
+			),
+		)
+	);
+	vc_assert_same( 'Middle East and Africa', $s[0]['name'] );
+	vc_assert_same( 'middle-east-and-africa', $s[0]['slug'] );
+	vc_assert_same( 7, $s[0]['term_id'] );
+	vc_assert_same( array( array( 'id' => '828', 'name' => 'Dubai', 'slug' => 'dubai' ) ), $s[0]['cities'] );
+}
+
+function test_validate_ok() {
+	vc_assert_same( array(), VC_Structure::validate( vc_fixture_structure(), vc_fixture_map(), array() ) );
+}
+
+function test_validate_unknown_city() {
+	$s                           = vc_fixture_structure();
+	$s[1]['cities'][0]['id']     = '999';
+	vc_assert_contains( 'City ID 999 is not a Viator destination.', VC_Structure::validate( $s, vc_fixture_map(), array() ) );
+}
+
+function test_validate_duplicate_city() {
+	$s                 = vc_fixture_structure();
+	$s[1]['cities'][] = array( 'id' => '737', 'name' => 'Amsterdam', 'slug' => 'amsterdam-2' );
+	vc_assert_contains( 'Amsterdam is listed more than once.', VC_Structure::validate( $s, vc_fixture_map(), array() ) );
+}
+
+function test_validate_duplicate_slug() {
+	$s            = vc_fixture_structure();
+	$s[1]['slug'] = 'paris';
+	vc_assert_contains( 'Slug "paris" is used more than once.', VC_Structure::validate( $s, vc_fixture_map(), array() ) );
+}
+
+function test_validate_bad_slug() {
+	$s                         = vc_fixture_structure();
+	$s[0]['cities'][0]['slug'] = 'amsterdam!';
+	$s[1]['cities'][0]['slug'] = 'New York';
+	$errors                    = VC_Structure::validate( $s, vc_fixture_map(), array() );
+	vc_assert_contains( 'Slug "amsterdam!" is invalid: use only a-z, 0-9 and -.', $errors );
+	vc_assert_contains( 'Slug "New York" is invalid: use only a-z, 0-9 and -.', $errors );
+}
+
+function test_validate_reserved() {
+	$s                         = vc_fixture_structure();
+	$s[0]['cities'][0]['slug'] = 'contact';
+	vc_assert_contains( 'Slug "contact" is reserved.', VC_Structure::validate( $s, vc_fixture_map(), array() ) );
+}
+
+function test_validate_taken_slug() {
+	$s                 = vc_fixture_structure();
+	$s[1]['cities'][] = array( 'id' => '22', 'name' => 'Victoria', 'slug' => 'victoria' );
+	$errors            = VC_Structure::validate( $s, vc_fixture_map(), array( 'victoria' => 'destination "Victoria"' ) );
+	vc_assert_contains( 'Slug "victoria" is already used by destination "Victoria".', $errors );
+}
+
+function test_validate_empty_region() {
+	$s            = vc_fixture_structure();
+	$s[0]['name'] = '';
+	vc_assert_contains( 'Region 1 has no name.', VC_Structure::validate( $s, vc_fixture_map(), array() ) );
+}
+
+function test_canonical_city_primary() {
+	vc_assert_same( 'paris', VC_Structure::canonical_city( vc_fixture_structure(), array( '479', '737' ), '479' ) );
+}
+
+function test_canonical_city_fallback_order() {
+	vc_assert_same( 'amsterdam', VC_Structure::canonical_city( vc_fixture_structure(), array( '678', '479', '737' ), '5555' ) );
+}
+
+function test_canonical_city_none() {
+	vc_assert_same( '', VC_Structure::canonical_city( vc_fixture_structure(), array( '5555' ), '' ) );
+}
+
+function test_primary_destination_id() {
+	vc_assert_same( '2', VC_Structure::primary_destination_id( array( array( 'ref' => '1' ), array( 'ref' => '2', 'primary' => true ) ) ) );
+	vc_assert_same( '', VC_Structure::primary_destination_id( array() ) );
+}
+
+function test_rewrite_rules() {
+	vc_assert_same(
+		array(
+			'^europe/?$'              => 'index.php?viator_destination=europe',
+			'^americas/?$'            => 'index.php?viator_destination=americas',
+			'^amsterdam/?$'           => 'index.php?viator_destination=amsterdam',
+			'^amsterdam/([^/]+)/?$'   => 'index.php?viator_tour=$matches[1]',
+			'^paris/?$'               => 'index.php?viator_destination=paris',
+			'^paris/([^/]+)/?$'       => 'index.php?viator_tour=$matches[1]',
+			'^boston/?$'              => 'index.php?viator_destination=boston',
+			'^boston/([^/]+)/?$'      => 'index.php?viator_tour=$matches[1]',
+		),
+		VC_Structure::rewrite_rules( vc_fixture_structure() )
+	);
+}
+
+function test_rewrite_rules_empty_region() {
+	$rules = VC_Structure::rewrite_rules( array( array( 'name' => 'Europe', 'slug' => 'europe', 'term_id' => 0, 'cities' => array() ) ) );
+	vc_assert_same( array( '^europe/?$' => 'index.php?viator_destination=europe' ), $rules );
+}