<?php query_posts( array (‘post_type’ => array( ‘hotel’, ‘museum’ ), ‘meta_value’ => $location_id) ); ?>
<?php echo GeoMashup::map( ‘map_content=contextual&cluster_max_zoom=50&zoom=11’ ); ?>
<?php wp_reset_query(); ?>
this works, but it looks in all meta-keys ;(