https://www.denver7.com/news/local-n...-control-tower

Stapleton International Airport air traffic control tower tours kick off Wednesday, November 14 and continue each Wednesday for the foreseeable future, a representative told Denver7.Registration is required and each ticket costs $10. Tickets to the first tour on November 14 appeared to have been snagged up fairly quickly, but you can check eventbrite.com for additional dates.
Organizers said the tower does not have elevator accommodations and the tour will require guests to climb 11 stories of stairs.