Monemvasia, Greece

In Monemvasia, known as the "Gibraltar of the East," discover an ancient castle and Byzantine churches, a monastery dating back to 1150 in the uninhabited Upper Town, and the Muslim mosque, which houses the city's archaeological collection and is located in the fortified Lower Town. Or travel inland to Mystras, the last Byzantine stronghold against the invading Ottomans, perched high on a Peloponnesian hill.