That's not an arch i don't believe. It appears to be a stunning circular raised edge around the wood pipe, which itself is amazing beyond belief. Then there's a raised circular brickwork edge right around the wood pipe. Like a double circle around the fitting for the pipe in the brickwork. So obviously it was part of the architectural design of the building, to include the wood pipe, because they made a beautiful emphasis with raised bricks that framed the wooden pipe. My brain is dancing with complete awe at what I i am seeing guys.
