Nicopolis ad Istrum

Nicopolis ad Istrum is an ancient Roman town in present-day north-central Bulgaria. Its remains are situated 18 km north of Veliko Tarnovo. Nicopolis ad Istrum is protected by rectangular defensive walls with gates in all four main sides. The principal western gate has a rectangular plan and is built of large ashlar blocks using the opus quadratum technique. It includes an outer double-leaf wooden gate and an inner descending gate, or portcullis.

A major project to repair and modernise the reserve began in December 2012.