The shrine of Raban Boya is a cave and lies in a little canyon in the mountains south of Shaqlawa. It dates back to the fourth century and was a mountain hermitage at the beginning. It is now a place for pilgrimage, especially for women, both Christian and Muslim, who appeal to Saint Boya to grant their fertility wishes.
https://www.mesopotamiaheritage.org/en/monuments/le-sanctuaire-de-rabban-boya-shaqlawa/
It takes about 1 hour to reach the cave. The first half of the path consists of paved stairs. The second half consists partly of loose stones and is difficult to walk.
The cache is not in the cave but on the way up. You are looking for a black glas container with a logsheet and a pencil.