Winchester Mystery House
Built in 1884, the San Jose residence of Sarah Winchester is a Victorian-style mansion full of architectural curiosities. Until her death in 1922, Winchester, the widow of a gun magnate, demanded continuous construction on the home to appease the spirits of those who died due to her husband's rifles. It's said to be haunted by those spirits as well as Sarah herself. The doors and stairs that go nowhere just add to the creepiness.
[Photo via Wikipedia]