In kaya, Megalithic sanctuary in Vrata, Bulgaria.

In Kaya is a rock massif about 6 m high dominating the Topolovski Prohod area, 4 km east of the village of Vrata. On its summit are four circular rock pits about 0.30 m in diameter, probably used to hold a wooden structure that closed a large natural opening in the rock. Fragments of Thracian pottery have been found at different levels of the site.

The site was registered in 2004 by archaeologist Ivan Hristov during a survey of the Sinyata Skala area. No archaeological excavations have been conducted, but Thracian pottery fragments found at different levels suggest cult use. Hristov links the ridge of which In Kaya is part to a branch of the route taken by Alexander the Great during his campaign against the Thracian tribes in 335 BC.

The name In Kaya means "blue rock" in Turkish. Ivan Hristov recorded the sanctuary in 2004 in the Sinya Skala area. He links the ridge of peaks from Kъz kaya to Momchil with a road branch used by Alexander the Great in his campaign against the Thracian tribes in 335 BC.

Bring plenty of water and wear sturdy footwear, as the site has no facilities and involves uneven, rocky terrain. Visiting during warmer months makes it easier to navigate the rough paths safely.

No excavations have been carried out at In Kaya; the site was registered in 2004 by the archaeologist Ivan Hristov during a survey in the Sinyata Skala area. Its cult character is inferred from the rock's shape and from Thracian pottery fragments found at several levels around the massif.