Different type of megalithic wall built like all of those type without any mortar. The stones are more irregular, but you cannot fit a razor blade in the joints. The hidden contact surfaces between the stones within the wall are mostly perfect fits without any filling or space in between. You find the exact same construction technology in the oldest Egyptian temples like in Giza and Abydos. That's different to Greek or Roman mortarless walls where the hidden stones surfaces are of concave shape with only the edges touching (anathyrosis).