The Stockholm Subway System is an amazingly varied art gallery spread over 100 stations, 47 of which are underground. The installations & works range from Romanesque statues to mosaics, murals & machine work.
One of the best place to visit in California - amazing Glass Beach. Glass Beach is one of the weirdest shores on Earth. It is located in MacKerricher State Park, near the military base of Fort Bragg, California.