The ridge — harju in Finnish — is a glacial esker that runs for about seven kilometres between two lakes, in places narrowing to a strip wide enough only for the road and a footpath. Pines grow straight out of the gravel and the water is visible on both sides at once. It is the kind of landscape Finns put on banknotes; in fact, an image of Punkaharju did appear on the old 100-mark note before the euro.
You experience it best by cycling or walking, not driving. There is a marked footpath that runs along the crest, with a few benches and viewpoints where the trees open. In winter the ridge is quiet, snow-loaded and slightly otherworldly; in summer it is busy with day-trippers from Savonlinna but the crowds thin out once you are more than a kilometre from the parking areas.
Bring a swimsuit. The water on either side is clean, cold, and shallow enough at the edges that you can wade in.