Lake Koman, in northern Albania, is a limestone canyon with the water turned up. The gorge was cut by the Drin long before anyone thought of a dam; in 1985 the river simply rose inside it. That is why it looks nothing like a reservoir: thirty-four kilometres of green water between walls several hundred metres high, narrowing at one point to just over fifty. The colour comes out of the rock — fine carbonate carried by the river, hanging in the water and throwing back green. What the water took was the valley floor and the road along it. The villages are still where they were, high on the slopes, stone houses showing singly or in twos above the waterline.
The boat that goes through is not a cruise. It is the road these villages do not have: cars are driven onto the open deck among crates, sacks and people going home, and the run to Fierzë takes two and a half hours. Midway the walls close in, the engine noise comes back off the rock at you, and for a minute there is no horizon in any direction you look. The lake has a job as well. Four turbines sit in a hall hollowed out inside the mountain, and almost all of Albania's electricity is made from water like this. A side channel with no road to it, the Shala arm, runs into shallows clear enough to show the gravel; the water is snowmelt, and cold enough to shorten your swim. In spring the limestone gives back what fell as snow, and thin falls come out of the walls, dry again by August. Graves opened beside a hillfort here in 1898 held objects made locally and in Byzantium, Sicily, Hungary and Crimea. The valley that looks sealed off never was, and the houses above the water are reached by nothing but a path down to a jetty and the boat you are standing on.