There are secret marble bathtubs waiting to be discovered by those lucky enough to have an insider connection on Capitol Hill in Washington, D.C.

The tubs were installed in the late-19th century. As reconstruction of the iconic Capitol Building was drawing to a close in 1858, a senator approached one of the engineers carrying a request from himself and 13 other colleagues: they wanted bathtubs. At the time, most senators camped out in boarding houses without indoor plumbing during the months Congress was in session.

As a result, six large Italian marble tubs were installed in the basement, the floor beside them covered in polished Minton tiles. By 1860, they were in full use and soon became a sought-after destination for politicians seeking a spot to relax, socialize, and write and memorize their big speeches. Senators would also share their luxurious tubs with guests, as a chance to indulge a hot soak was a rare privilege. According to the Senate’s website, one user accidentally insulted a female visitor after inviting her to go down into the basement to bathe. She reportedly fled the building.

However, the rise of indoor plumbing eventually rendered the bathtubs obsolete. By 1890, all but two were removed. They fell into disrepair and were eventually forgotten.

The two surviving tubs were rediscovered during an excavation in 1936, to much confusion. Architects and political staffers struggled to solve the mystery of the basement bathing vessels until a man named Abraham Lincoln Goodall stepped forward and offered his account of using the tubs as a boy. His memory helped historians piece together the forgotten past of the mysterious marble tubs.

Now, those who are guests of Capitol Hill staff can head down into the boiler room that houses the tubs. To get there, find the security office, wind past some twisted stairs, and go into the bathroom that has since been converted into a boiler room. Make sure you knock and check for a light. Security officers still use the running water, only now for toilets.