Lake Biwa, Japan's largest freshwater lake, sits just over the mountains from Kyoto in neighbouring Shiga Prefecture — close enough for an easy day trip, and different enough in character (open water, lakeside towns, a genuine sense of space) to feel like a real break from Kyoto's dense temple circuit.
Hikone Castle
One of only a handful of Japanese castles with an original keep surviving intact from the feudal era — most surviving "castles" elsewhere in Japan are concrete reconstructions, which makes Hikone's genuine wooden interior a rarer thing to see. The castle grounds and surrounding Genkyū-en garden are a worthwhile stop in their own right.
The lake itself
Lake Biwa is large enough to feel more like a small inland sea than a lake — boat cruises operate from several points around the shore, and the lakeside towns have a noticeably slower, more residential pace than central Kyoto.
Ōtsu
The prefectural capital, Ōtsu, sits directly on the lake's southern edge and makes a reasonable base for a shorter visit if Hikone feels like too much added travel time — closer to Kyoto, with its own lakeside temples and a more compact town centre.