Three feet below the aluminum lightning rod at the tip of the Washington Monument, a small panel in the marble allows workers to climb out from inside the obelisk.
The access hatch was installed so that minor repairs can be made to the monument without the need for massive scaffolding. Instead, daredevil National Park Service employees can worm their way out the access hatch, loop ropes over the apex and rappel down the tower. This capability came in handy after the 2011 earthquake when NPS used it to check for structural damage.
The panel is painted white and is nearly impossible to spot from the ground without binoculars. See if you can pick it out on the eastern side of the monument that faces the Capitol Building.
You can watch a timelapse of the rappelling routine here.