The structure collapses.

1000 years after people; A millenium after humanity's disappearance Rome's Colosseum still stands, even after most modern building's have fallen. The Colosseum owes its longevity to the lack of reinforcing rebar in its concrete. But ten centuries of plant growth have weakened the Colosseum's concrete and a moderate earthquake finally brings down the home of the gladiators.

The structure filled with weeds.