The Sumug fortress sits on a low hill at the edge of Ilisu village, commanding a view down the Kurmukchay valley. It is a four-storey defensive tower, built sometime in the 17th or 18th century — the exact date is uncertain, and no one is sure by whom. The stonework is solid enough that it survived more or less intact; the interior now holds a modest branch of the Qakh History Museum with exhibits on the Elisu Sultanate.
The fortress is the defining landmark of Ilisu and the obvious first stop in the village. The climb to the top rewards you with a panoramic view of the gorge and the mountains beyond. Entrance is inexpensive; a caretaker is usually on site during daylight hours.