Iskanderkul is a triangular lake at 2,195 metres in Tajikistan's Fann Mountains, dammed by a fallen mountainside, and it carries the Persian form of Alexander's name. Local lore holds that Alexander's warhorse Bucephalus never left this water, and that on full-moon nights a white horse rises out of it to graze the shore. Historians are unmoved: Bucephalus died in what is now Pakistan, and Alexander is not thought to have come this way. Older sources call it Mashtonzardarya; the name Iskanderkul only shows up in Russian writing in the later nineteenth century. The colour is rock powder off the bare peaks, deepening to turquoise on clear autumn days once the silt has settled.
The way in is a rough track off the Dushanbe–Khujand highway, twisting down the gorge with the water showing and vanishing behind each bend. At one point it ducks under a huge boulder wedged overhead. Then the gorge ends and you come out under the peaks at full height. You pitch on the open shore a few steps from water that stays under ten degrees even in August, straight off the snow. A shaded trail takes you along the shoreline through birches tied with strips of cloth, prayers left by local visitors. A few hundred metres from where the Sarima stream comes in, a smaller lake sits inside a ring of trees: Kul-i Moron, the lake of snakes, and it warms through by afternoon as the big one never does. Three rivers empty into Iskanderkul and one narrow outlet drains the whole basin. A short walk down from it the whole outflow funnels into a gorge and drops in the fall the locals call the Fann Niagara, watched from a platform at the lip where the ground moves under you. That outlet keeps going. It joins the Yaghnob, becomes the Fan Darya and feeds the Zeravshan, the river that watered Samarkand and Bukhara. A tenth-century geography already named this lake as the head of the Bukhara river, a thousand years before anyone hung a conqueror's name on it.