Minecraft wiki entry for Ocean_Monument, associated text: The monument is constructed entirely from variants of prismarine and lit by sea lanterns. It includes a large central section flanked by two wings. Under the monument are 23 giant pillars that stretch to the ocean floor. The main entrance is located at the front of the central section. The base size of the structure is 58×58 blocks. Thus, the ocean monument (the location where guardians and elder guardians spawn) area is 3,364 square blocks.