PARIS — Everyone knows the Eiffel Tower. But very few are aware that it houses a secret apartment, built by Mr. Eiffel himself.

According to Cosmopolitan, Gustave Eiffel, who completed his iconic tower back in 1889, included a secret nook on the third level. At the time, he furnished the room with wooden furniture and a grand piano, as well as a small laboratory outfitted with scientific equipment.

When word spread among Parisian high society about Eiffel’s apartment, the famed designer received numerous requests to rent it out, even for a day. He declined each and every time, allowing no one to ever see his private oasis.

Now 92 years after his death, the apartment remains closed to the public, with only a rare opening every once in a blue moon. Although chances are slim of ever getting a sneak peek inside, it’s exciting to know that high above the City of Lights there exists a small room where time has stood still.