Eiffel Tower was to be dismantled in 1909, when its ownership would revert to the City of Paris. The City had planned to tear it down (part of the original contest rules for designing a tower was that it should be easy to dismantle) but as the tower proved to be valuable for communication purposes, it was allowed to remain after the expiry of the permit. Eiffel made use of his apartment at the top of the tower to carry out meteorological observations, and also used the tower to perform experiments on the action of air resistance on falling bodies. For the
Philadelphia City Hall 1871 to 1901 at a cost of $24 million. City Hall's tower was completed by 1894, although the interior wasn't finished until 1901. Designed to be the world's tallest building, it was surpassed during construction by the Washington Monument and the Eiffel Tower. Upon completion of its tower in 1894, it became the world's tallest habitable building. It was also the first secular building to have this distinction, as all previous world's tallest buildings were religious structures, including European cathedrals and—for the previous 3,800 years—the Great Pyramid of Giza. With almost 700 rooms, City Hall is the largest municipal building