We present a system for exploring large collections of photos in a virtual 3D space. Our system does not assume the photographs are of a single real 3D location, nor that they were taken at the same time. Instead, we organize the photos in themes, such as city streets or skylines, and let users navigate within each theme using intuitive 3D controls that include move left/right, zoom and rotate. Themes allow us to maintain a coherent semantic meaning of the tour, while visual similarity allows us to create a "being there" impression, as if the images were of a particular location. We present results on a collection of several million images downloaded from Flickr and broken into themes that consist of a few hundred thousand images each. A byproduct of our system is the ability to construct extremely long panoramas, as well as image taxi, a program that generates a virtual tour between a user supplied start and finish images. The system, and its underlying technology can be used in a variety of applications such as games, movies and online virtual 3D spaces like Second Life.