Here is something I have used a few times. Yahoo Research has a TagMaps project, WorldExplorer which shows main tags for any place and pictures.
One can quickly decide what to visit in a place.
And here is an interactive Flash widget for Peru.
One of the researcher behind this is Mor Naaman
Try India and San Francisco, see if you can find Yoga in the Presidio or find out why Machu Pichcu does not show up in Peru.