1 day after people: The lights go out in Paris, and so does the power in the Eiffel Tower.
10 years after people: The lifts of the Eiffel Tower cannot hold by their cables any longer. One lift falls to the ground, triggering a chain reaction of all four to smash down to the ground.
100 years after people: The Mona Lisa is swollen and cracked, being painted on wood. In the time of humans, sensors would detect the movement equivelant to that of 1/100th the width of a human hair. But when the power failed, so did the motion sensors. The painting is eaten away by deathwatch beatles.150 years after people: The Arc De Triomphe is covered in greenery, though it is still standing. But all it takes to knock the famous gateway down is a heavy rainstorm.
200 years after people: The head of the Eiffel Tower collapses, but the legs remain. They will be here for another 500 years, but eventually, the Earth will swallow them up too.
800 years after people: The Louvre Museum has collapsed. Its walls opened liked a book, tearing the ceiling apart in the process. But, the famous Venus De Milo sits among the rubble. It could last for hundreds of years.
2000 years after people: The Cathedral of Notre Dame is the last building still standing in Paris, as it is now a swamp. But, it has cheated death. The long reign of the Notre Dame comes to an end, when the Eastern Wall fails. The other walls cannot support the roof of the building alone. More walls collapse, pulling a famous landmark down into the swamp.