add_filter( 'rank_math/json_ld', function( $data, $jsonld ) {
    if ( isset( $data['publisher'] ) ) {
        $data['publisher']['areaServed']['@type'] = "city";
		$data['publisher']['areaServed']['name'] = "Madrid";
		$data['publisher']['areaServed']['sameAs'] = "https://en.wikipedia.org/wiki/Madrid";
    }
    return $data;
}, 99, 2 );