Washington (CNN) -- It may look like an action movie being shot on the National Mall Tuesday, but in fact it will be architect/engineers at work, rappelling down the sides of the Washington Monument, looking for damage caused by the August earthquake.
The National Park Service announced Monday that experts have completed an interior assessment of the monument and found it to be structurally sound.
"The heaviest damage appears to be concentrated at the very top of the monument, in what is called the pyramidion, where large cracks of up to 1 1/4 inch wide developed through stone and mortar joints," said Bob Vogel, superintendent of the National Mall and Memorial Parks. Daylight is visible through some of the cracks, and a substantial amount of rain water has gotten into the monument, which could cause further damage.
To get a closer look at the outside of the structure, architect/engineer/rappellers from the firm of Wiss, Janney and Elstner, the architectural firm hired by the National Park Service, will scale the outside of the structure to get a closer look.
Their "difficult-access team will install climbing ropes and safety lines on all four sides of the monument, then clip on to those lines and exit the monument from the windows at the observation level," Vogel said. Weather permitting, they will climb up the pyramidion and then descend the length of the monument looking for exterior damage.
On Monday, the National Park Service put on its web page dramatic video of the interior of the monument when the earthquake took place. It shows park rangers and tourists rushing down the stairs as debris falls on the observation deck.
Once the exterior assessment is complete in the next few weeks, the Park Service expects to come up with a timeline to reopen the monument to the public.
The Washington Monument, built between 1848 and 1884, is 555 feet, 5 1/8 inches tall. Its walls are 15 feet thick at the base and 18 inches at the top, and are composed primarily of white marble blocks, according to the National Park Service.
"The monument is structurally sound and is not going anywhere," Vogel said. "It is a testament to the original builders that the monument has withstood not just this earthquake, but an even larger one in the late 1800s."