The Sydney Opera House is one of the most iconic structures on the planet thanks to the magnificent shell-shaped roof. The structure is supported by 580 concrete pillars that are sunk 25 meters below sea level, but a week after people saltwater from the Sydney harbour begins to erode the pillars in the splash zone at the same time the moist and salty air begins to attack the tiles that cover the shells.
35 years after people:
Lightning strikes Sydney. A fire starts. Luckily a rainstorm put it out before it did major damage to the Sydney Opera House.
75 Years after people:
In Sydney Harbour the Opera House is becoming unstable because the salt air has taken off the mosaics of shells and waves have eroded the pillars. The final blow is when the prefabricated cables that help to the shells sitck together break and an entire shell collapses, the most exposed pillars fail and the rest of the structure collapses and sinks down under, to the bottom of Sydney Harbour.