The escalators at Dupont Circle Station on the Red Line of the Washington Metro are 188 ft (57 m) long. I think it's the longest escalator I've ever seen. From what I hear, it's not even the longest in DC. Update (10/29/09): Another station has an escalator that is 155 m long (that's about 1.5 football fields long!) (thanks ajpresto714) View On Black
