Lake Orestiada is the reason Kastoria looks the way it does. The city's peninsula juts out into it, giving views over the water in almost every direction from the old part of town. The lake is shallow and warm in summer, ringed by reeds and wetland vegetation, and forms an important habitat for water birds — herons, egrets, and cormorants are common along the shores.
Walking the full circuit of the lakeside road is one of the best ways to experience Kastoria. The eastern shore is quieter and leads to the Panagia Mavriotissa monastery at the tip of the peninsula; the western shore passes the fur warehouses and workshops before reaching the narrow isthmus that connects the peninsula to the mainland. The full circuit takes two to three hours on foot.
Boat trips on the lake operate from the waterfront near the town centre in summer. Kayak rental is also available. In winter the lake occasionally freezes over — a remarkable sight given the backdrop of mountains.