The imposing Cerven fortress is reached via steps dug out of the rock. Built in the 12C, this medieval citadel replaced a former Byzantine stronghold dating from the 6C. In its heyday, it sheltered within its enclosure eleven churches, three palaces and a feudal castle. Its purpose was to safeguard the access to Veliko Turnovo. All that remains of this formidable city perched on a promontory surrounded by the river is the keep, a symbol of the power of the place in the past.