The interior is occupied by iron stairs that spiral up the walls, with an elevator in the center, each supported by four iron columns, which do not support the stone structure. The stairs contain fifty sections, most on the north and south walls, with many long landings stretching between them along the east and west walls. These landings allowed many inscribed memorial stones of various materials and sizes to be easily viewed while the stairs were accessible (until 1976), plus one memorial stone between stairs that is difficult to view. The pyramidion has eight observation windows, two per side, and eight red aircraft warning lights, two per side. Two aluminum lightning rods, connected via the elevator support columns to ground water, protect the monument. The monument's present foundation is thick, consisting of half of its original bluestone gneiss rubble encased in concrete. At the northeast corner of the foundation, below ground, is the marble cornerstone, including a zinc case filled with memorabilia. Fifty American flags fly on a large circle of poles centered on the monument. In 2001, a temporary screening facility was added to the entrance to prevent a terrorist attack. An earthquake in 2011 slightly damaged the monument, and it was closed until 2014. It was closed again for elevator system repairs, security upgrades, and mitigation of soil contamination from August 2016 to September 2019.