With things like Street View, satellite images, aerial images and so on, you can see for yourself what any corner of the planet looks like any time you feel like it. But you can't go everywhere and, for the most part, you can't go inside buildings.
However, while there may a while before you'll find the interior of every building in the world in Google Maps, you can already get into more places than you'd imagine courtesy of Instagram and its 100 million users.
Users who take photos everywhere they go and post them on Instagram for everyone to see. The same photos are visible publicly on the web as well and via the Instagram API.
And since most of them are geo-tagged, it's not hard to figure out how you could use them to scour the world.
isn't the first service to leverage Instagram's increasing pool of photos, but it's the first to do in a way tied to actual places, thanks to the Foursquare API.
All you have to do is pick a city, search for a location and see whether someone has posted photos from inside. Chances are, for popular places at least, you'll find some interesting shots.