The Eiffel Tower stands on the left bank of the Seine in Paris, capital of France. It is 317 meters (1040 ft) tall, 125 meters (410 ft) wide, and consists of 7,300 tonnes of iron. The tower was designed by Gustave Eiffel as an entry to a contest that was launched in 1889, in honor of the 100th anniversay of the French Revolution.
The tower was based upon the principle of building bridge supports. It was decorated by architect Stephen Sauvestre, who among other things came up with the idea of the arches at the base. The construction of the Eiffel Tower was completed in no more than 22 months, a record time.
Astonishingly, the tower was meant to last just 20 years, but experiments such as using it for radio signals and transmissions saved it from demolition. Nowadays Paris or even France is unimaginable without the iconic Eiffel Tower. Each year thousands of people travel to Paris just to see it, it's been featured in numerous movies, and images of the tower have been produced and distributed in gigantic quantities worldwide.
official website you'll find the app, the online ticket shop, and loads of information. And if you a prefer a guided tour over an app, there are plenty of options to choose from. You can compare prices and features here and here.