There are ruins, scattered about the world, and all are sealed with unbreakable locks.
When all of these locks suddenly open, what emerges?
A cave with weapons sunken into the walls, blades sticking out of the floor and ceiling, and so on. Possibly, any weapon used in it could be torn out of the hand and sink into the stone.
"...the city was built on many levels, linked by stone bridges. But with the improvements in diet and corresponding increase in stature and strength of the populace, these bridges became too low, and the people would hit their heads. The bridges were eventually done away with in 1764, but the scars on the walls where they once jutted out remain, and in Low Bridge Street there is still one extant bridge, measuring about 6' high." - Chronicler Rasill, Mondopedia, Vol II (The Lands of Hyellia)