Back in the days before burglar alarms, how did you know if strangers were in the house? Nijo-jo, with ingenious cunning right out of a ninja movie, was built with a “nightingale floor”: The smooth wooden planks of the walkways chirp when weight lands on them. Nijo-jo is technically a castle (hence the "-jo”) but it’s really more of a very rich person’s estate, defended only by low walls, a moat, and a tower or two—and those floors. Originally built by Tokugawa Ieyasu in 1603, it’s now an oasis in central Kyoto, with a gorgeous traditional garden. Try to arrive in the early morning or late afternoon; it’s one of Kyoto’s most popular attractions and a UNESCO World Heritage Site, and can be jammed.