Lake Ohrid is one of the oldest lakes on Earth, a sheet of water in the mountains between North Macedonia and Albania that has been filling its basin for more than a million years, so clear that you can see twenty metres down, with a medieval town stacked up the cliffs on its northern shore. The town is Ohrid, and its stone lanes climb from the old harbour past Byzantine churches to Samuel's Fortress, built in the late 900s when this was the capital of a Bulgarian empire; the battlements were rebuilt in 2003 where nothing had survived, but the view down over the roofs to the lake is the one the fortress was built for. On the way up the lanes pass a Hellenistic theatre that the townspeople buried after the Romans used it for executions, found again by accident in the 1980s. In the ninth century the monk Saint Clement ran a school here that taught thousands to read and write, an early cradle of the alphabet now called Cyrillic.
The lake is walked at the waterline. A plank boardwalk pinned to the rock runs from the harbour below the cliffs to the Church of Saint John at Kaneo, a small thirteenth-century church on a rock above the water, the picture of the place. The narrow wooden boats pushing off from the harbour in the morning are working boats after Ohrid trout, a fish found in this lake and nowhere else, one of many creatures that evolved here in isolation. A boat runs down to the southern end, where dozens of cold springs bubble up through the lakebed beside the monastery of Saint Naum; the water comes from Lake Prespa, 150 metres higher on the far side of the mountain, which has no outlet and drains underground through the limestone to surface here. The springs keep the deep water cold all year, but the shallow bays warm enough to swim by June. Ohrid has been a town for two and a half thousand years, and the lake it looks at is a thousand times older.