Windsor, United Kingdom
The Crooked House of Windsor,
also known as the Market Cross House, was built in 1592. It features a now-blocked secret passageway that leads to Windsor Castle and is said to have been used for trysts between King Charles II and his mistress. The house didn't start to tilt until 1718 after it was restructured with unseasoned green oak. The building now functions as a tea house for patrons who don't mind sitting at a bit of an angle; the crooked floors were never leveled.