Eiffel had a permit for the tower to stand for 20 years; it 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 demolish) but as the tower proved valuable for communication purposes it was allowed to remain after the expiry of the permit. Eiffel made use of his apartment at the top level of the tower to carry out meteorological observations, and also made use of the tower to perform experiments on the action of air resistance on falling bodies.