Loch an Eilein — "the loch of the island" — is one of the loveliest small lochs in the Scottish Highlands: a dark, peaty stretch of water in Rothiemurchus Forest, with a ruined fourteenth-century castle on a small island at its heart and ancient Scots pines reflected in the still surface. A 5-kilometre path circles the loch through the old forest, making it one of the finest and most accessible short walks in the Cairngorms National Park.
The walk takes about an hour and a half at a gentle pace. Ospreys nested on the castle island until 1899 — they have not returned, though they can sometimes be seen fishing on the loch in summer from the osprey viewing point near the visitor centre. Red squirrels are reliably present in the pines along the north shore. The loch is three kilometres south of Aviemore and reached by a single-track road through the forest.