When making a trip to Frankfurt we were delighted to find a branch of Veggie House there as well (and fairly close to the main train station). Frankfurt Veggie House does the famous (well it should be) UFO pizza which is a pizza, topped with another pizza.
Sfizy Veg Berlin
..apparently europe's first vegan pizza place!
Haven't been myself yet, but a friend of mine has his studio around the corner and says it's superb!