Greece: Ancient Olympia

When western travelers got into the depth of the Peloponnesus peninsula and found the remains of Mystras, they though it was Ancient Sparta (Sparta actually lies at the foothills of Mystras and not much remains from it). Mystras was a fortified hilltop town during the Byzantine era, the largest and best such medieval fortress in Greece. The little Kingdom was known as Byzantine Morea and was ruled by successive Despots of Morea for about 200 years in the 14-15th centuries before the Ottoman Empire came. The last Byzantine emperor, Constantine IX, was the Despot of Mystras before ascending to the throne. Mystras has a stunning location on the slopes of Taygetos mountain with buildings and medieval churches and monasteries scattered around on the way up to the acropolis on the top. Several of the monasteries, especially Perivieptos and Pantanassa, have stunning well preserved 14-15th century frescos adorning their ceilings and walls. It takes some not-trivial strenuous hiking to explore this UNESCO World Heritage Site.