1. Eiffel Tower, Paris, France

Built in 1889, the Eiffel Tower remains the most well-known tourist destination in Paris, France.

Eiffel Tower

2. Niagara Falls, Canada and United States

Okay so not necessarily under construction but, on March 29, 1848 the flow of water was stopped over both American and Canadian falls due to an ice jam in the upper river. People could walk out on the cliff above the falls for that short period of time!