The Terracotta Army in Xian, China dates back to the 3rd century B.C. In 1974, farmers working in the area dug up the statues. There is now a massive metal roof protecting the statues from the elements... at least for now.
1 day after people: The power grid fails in China. The lights go out at the Terracotta Army.
6 months after people: Rain and snow damage the metal roof and soon holes open up.
1 year after people: The holes in the roof allow water to get inside flooding the walkways and eroding the details on the sculptures.
10 years after people: The water inside the structure has rusted the bottom supports of the roof and the middle skylight has broken letting water attack the top of the trusses supporting the roof.
25 years after people. The first statues are now falling apart. The fine details were eroded away long ago and now water is eating away at the base of the statues causing them to fall and smash on the ground.
50 years after people: China has earthquakes on a regular basis which is bad news for the Terracotta Army. An earthquake measuring 7.0 on the Richter Scale shakes Xi'an. Then, one of the arches holding up the roof falls, then another and another. In 10 seconds, the roof collapses crushing the famous soldiers below.