|The Vatican, a major cluster for geo-tagged Wikipedia entries. Clearly a number of the worshippers and tourists are checking in with Foursquare.|
|Saint Marco's in Venice, very much like Vatican but also a huge cluster of Flickr images. So this is not only a popular tourist attraction, but one clearly judged highly for its visual beauty and not just its meaning. |
To conclude, we can guess that a lot of people go to the Vatican for religious purposes as well as tourism, but that the square around Saint Marks is not seen as a religious site as much as a work of art which many higher end photographers share with the premium Flickr service.