Kiev Pechersk Lavra
Also known by its English name—the Monastery for the Caves—this 11th-century monastery complex houses both a huge cultural museum and an active monastery. The monastery is easily recognizable on the Kiev skyline thanks to its gilded dome-topped bell towers and churches, most of which were built (or rebuilt) in the 17th and 18th centuries. However, it's the monastery's labyrinthine subterranean cave system—full of narrow passageways and even a few mummified monks—that most visitors write home about. The lavra also houses one of the largest museum collections in the city, featuring religious items, books, and textiles.