Ogof Dydd Byraf is a cave which extends under Esclusham Mountain in the north-east Wales from its entrance in the south face of the Minera Limeworks quarry.

[2] After a short series of mined passages there is a narrow 10 metre pitch into the main levels consisting of a series of well-decorated galleries.

Some of the passages come very close to the cave Ogof Llyn Du whose access is blocked by a deep and difficult sump.

Over the years this cave had been under threat by the quarry operations,[3] but it is now protected as an SSSI.

[4] and owned by North Wales Wildlife Trust[5]