Using 3D Photo Tours, users will be able to take a tour of places like the Grand Canyon, Buckingham Palace, Fenway Park, Trevi Fountain and many more, you can see this list of all the places for which 3D Photo tour is available.
You can also take a virtual 3D visit to the seven wonders of the world here
Here is how Google developed 3D Photo Tour :
"To produce these photo tours, we use advanced computer vision techniques to create a 3D experience from public, user-contributed Picasa and Panaromio photos. We start by finding clusters of overlapping photos around major landmarks. From the photos, our system derives the 3D shape of each landmark and computes the location and orientation of each photo. Google Maps then selects a path through the best images, and adds 3D transitions to seamlessly guide you from photo to photo as if you’re literally flying around the landmark and viewing it from different perspectives. "
Watch this video to learn more about 3D Photo Tour