A Late Antique and Medieval fortress, located on a rocky promontory less than 1 km southeast of the modern village of Širokovo (Широково, also rendered Shirokovo). The site is called Kale Širokovo or Kale burun and is triangular, located between the Černi Lom and Baninski Lom rivers, which join north of it. The fortress had three layers of defenses and a moat in front of the outermost walls. A larger unfortified settlement occupied the area of modern Širokovo, defended by this fortress from the south. The town and fortress are recorded as Kiristafça in the narrative of the Ottoman conquest in 1388.
https://www.bulgariancastles.com/s-shirokovo-krepost-kale-burun/
https://archaeologynewsnetwork.blogspot.com/2020/10/archaeologists-uncover-unique-roman.html