The pyramid of Cestius was built in Rome around the beginning of the first millennium. It was a tomb for a wealthy man who had held several offices. It was looted, and later built into the fortification walls of the city. It was discovered much later, and excavated from the wall. It is something like 40 meters tall. It looks much smaller in this picture taken some time before October, 1938, when this picture was published in a book that consisted of architectural renderings of a parade route, lavishly decorated for when the Fuhrer would visit Rome.
However much I detest the fascism & the Nazis, I have to admire the artistry of the following painting. The book was in black and white; I snapped this with my phone. If you could edit out the flag in front, it would be awesome. So ignore the nazi flag, look at the castle with torches on all the ramparts. Look at the body of horsemen before the pyramid. Are they knights or cloaked figures? This looks like an exceedingly evil stronghold even without the flag. It is actually hellish, depicting a black sky, vast flames over the castle, an alliance with unspeakable horrors inside the pyramid.
This would be an awesome location in Hell, or your campaign’s Mordor or whatever. Muspelheim, I’m thinking for mine. Crack the castle to get to the entrance of the pyramid (really a vast obelisk, only the tip is visible). Delve the tombs. Get MacGuffin. Escape.