This is roof of the Führerbunker, beyond any doubt!a platform rising up out of the Reichschancellery Garden.
Early post-war photo shows top soil excavated and a side of the concrete slab roof exposed as per Christoph message (circled in yellow).
It also shows unfinished second conical tower (just left to bunker exit/entry).
Next photo taken after partial demolition shows the soil dump (from top and side excavations) in front of the bunker.
Side excavation of bunker top concrete slab (with the exception of March 1945 repairs) were done after the war, during demolition work.
It was nearly impossible to dismantle this structure from the top - it was built to exactly prevent that - so it was tackled from the side as shown on the next photo.