Koshoy Korgan (Koshoy's fortress) is a 250m square of muddy wall remnants from what is thought to have been a powerful 12th-century Karakhanid citadel, constructed on a site inhabited since at least the 8th century. Walk the path that follows the tops of the old ramparts, past the western-wall remains of a minaret and the southern-edge excavations of what is claimed to be Koshoy's home.
Just before the entrance is a museum which has a striking design and an attractive art collection alongside artefacts from historic sites across Naryn oblast. However, it's rarely open, so worth calling ahead to check. The site is 3km off the main road from Naryn to Torugart at Km409: head 800m down Köchör, the easternmost street in Kara-Suu village, then left on Abit (at Köchör 44/Abit 33) which curves around to the site.