The Bas-Relief

Every 23,375 days, exactly at 12:04PM - at exactly 64 equal rotations of the plane - at zero degress latitude, and zero degrees longitude, the tide of the ocean will suddenly drop. A building roughly the size of three city blocks, covered with bas reliefs, will rise suddenly from the depths.

This building will then begin to sink immediately, and will submerge completely within 2 minutes. According the eyewitness accounts, the reliefs depict certain famous events in human history, including events that had not yet happened.