21.9170°N, 31.2830°E.
Middle Kingdom Egyptian fortress on the west bank of the Nile near the second cataract, built in mud-brick and stone during the reign of Senusret III around 1860 BCE. Buhen Fortress was the largest of the cataract forts, enclosing roughly 13,000 square metres behind walls that rose 10 metres and were 5 metres thick at the base, equipped with bastions, a dry moat, loopholed parapets, and a covered way to the river. The garrison administered river traffic and gold shipments from the mines of the Wadi Allaqi. Excavations by Walter Bryan Emery for the Egypt Exploration Society between 1957 and 1964 documented the structure in detail before it was inundated by Lake Nasser in 1964. Some painted wall fragments and a small reconstructed gate were salvaged to the Sudan National Museum in Khartoum.
A piece of fortified Bronze Age engineering as sophisticated as any medieval European castle now lies under the reservoir.