An eight-foot-deep sinkhole opened up on a street in front of the Pantheon in Rome, revealing several ancient paving stones dating as far back as 27BC.
The area had been closed to the public at the time so no one was injured, but during tourist season the event could have caused much more damage.
The paving stones were unusually well preserved because they were mostly surrounded by pozzolan, a type of dirt with significant amounts of silicon dioxide that absorbs excess moisture and can help prevent rot.