Perched on a rocky peak, Asen Fortress is a real vertigo-inducing citadel, built in 1230 by Tsar Ivan Asen II. A path, dug out of the rock, leads to a steep promontory and to the splendid Byzantine church of Our Lady (Sv. Bogorodica). Built in the 12C and 13C, it has retained beautiful murals. The path continues as far as the remains of the fortress itself: sections of the curtain walls and a ruined tower. From there, the view of the narrow valley and of the summits of the Rhodope mountains is breathtaking.