London dominates the top 10, with the London Eye coming in fourth place and Tower Bridge in seventh. New York is the only other city with more than one landmark in the top 10 (Empire State Building in fifth and Statue of Liberty in eighth).
You can see the map, with the full top 50 here.
The top 10 were:
1) Eiffel Tower, Paris. #EiffelTower, used 3,411,588 times.
2) Big Ben, London. #BigBen, used 2,436,319 times.
3) Grand Canyon, Arizona. #GrandCanyon, used 1,938,482 times.
4) London Eye, London. #LondonEye
5) Empire State Building, New York City. #EmpireStateBuilding, used 1,578,349 times.
6) Golden Gate Bridge, San Francisco. #GoldenGateBridge used 1,572,846 times
7) Tower Bridge, London. #TowerBridge used 1,178,399 times.
8) Statue of Liberty, New York City. #StatueOfLiberty used 1,083,079 times.
9) Sagrada Familia, Barcelona. #SagradaFamilia used 929,310 times.
10) Colosseum, Rome. #Colosseum used 866,195.
Of course, this only shows pictures when people use the hashtag,people may upload pictures without the hashtag or different one (such as #eiffeltowerparis).