Petrič Castle

An Ancient, Late Antique, Medieval, and Ottoman fortress located 5.4 km north-northwest of the modern village of Avren. Numismatic and ceramic remains, among ample other finds, date to the 3rd through 15th centuries. Petrion or Petrin are Greek toponyms, corresponding to the Slavic name Petrič (Петрич, also rendered Petrich). The fortified settlement was mentioned as Petrion by Manouēl Philēs in a poem commemorating an expedition of Mikhēl Glabas Tarkhaneiōtēs in 1278, and as Petrin in Constantinopolitan patriarchal documentation from 1369. The narratives of the Varna Crusade, which destroyed the fortress in November 1444, name it as Petrus, Petrecz, and Peterspurkt.

https://www.bulgariancastles.com/s-avren-krepost-petrich/