Hi gozdecennet,
it's the inlet (or outlet) of a tunnel for a aqueduct which is under construction. See https://www.openstreetmap.org/way/1143979998 , https://www.openstreetmap.org/way/1143965489 and https://www.openstreetmap.org/way/1143973884 ass well.
Greetings,
lyctkel
