On January 6, a mob of about 800 stormed the U.S. Capitol in support of former President Donald Trump, and many people made quick assumptions regarding who the insurrectionists were. Because a number of the rioters prominently displayed symbols of right-wing militias, for instance, some experts called for a crackdown on such groups. Violence organized and carried out by far-right militant organizations is disturbing, but it at least falls into a category familiar to law enforcement and the general public. However, a closer look at the people suspected of taking part in the Capitol riot suggests a different and potentially far more dangerous problem: a new kind of violent mass movement in which more “normal” Trump supporters—middle-class and, in many cases, middle-aged people without obvious ties to the far right—joined with extremists in an attempt to overturn a presidential election.

The U.S. Capitol Crypt is home to 40 oric columns, a dozen statues, and no human remains. It’s also a lot less far off the beaten track than your regular run-of-the-mill underground vault—visitor tours of the Capitol building pass through it on a daily basis.

In fact, the Capitol Crypt wasn’t exactly intended as a crypt. According to Architect of the Capitol, the building’s first architect, r. William Thornton, called it a “Grand Vestibuleȁ on a blueprint from 1797. Nine years later, his successor dubbed it the “General Vestibule to all the Offices.ȁ But while the room was mainly meant to function as a thoroughfare, it was also supposed to be the final resting place of George Washington and his wife, Martha.

After Washington died in 1799, Congress decided it would be fitting to entomb him in the Capitol. Though Washington’s will expressed his wish to be interred at Mount Vernon, Martha considered it her “public dutyȁ to grant Congress permission to move him. Architects altered the Capitol building plans to make room for a tomb below the so-called “Grand Vestibule,ȁ which itself was below the Rotunda (the extravagant circular chamber beneath the Capitol dome). A statue of the first president would sit atop the tomb, and a 10-foot hole in the vestibule’s ceiling would allow people in the Rotunda to look down on it.