shows nicolette on the observation level as high up in the monument as visitors can go.aiting to take a group of about 20 tourists down in the elevator. >> as i'm sitting there, the elevator actually starts to make noise. >> she realizes immediately something unusual is happening. >> i know the elevator's noises and these are loud banging sounds, then the walls of the elevator begin to vibrate. >> the monument begins to shake dramatically, nicolette doesn't know what is happening, but she knows staying on the observation level is probably not a good idea. >> we're 500 feet up in the air. the windows don't open. the only way to go is down. so i jump off the ledge, i run down that stairwell. and that next level, there's an emergency exit for the stairs. i open the door to get the visitors down. >> debris rains down on the fleeing tourists. the building is rocking so violently, it almost knocks the ranger off her feet. >> i'm terrified. i'm thinking, i don't know if i'm going to get to the bottom of this stairwell, i really think there's going to be something to knock the w