One of the things it had were downtown pedestrian shortcuts. For example, starting at the ferry terminal, you could walk up the Marion street overpass to 1st Avenue, enter the lobby of the Federal Building, take the elevator to the 4th floor, and exit to 2nd Avenue. Cross the street and take the escalator to First Interstate Plaza and walk through that to 3rd Avenue. Across the street was the Seafirst Building. You could take the 3rd Avenue entrance to that, ride its escalators up, and take its 4th Avenue exit. Cross the street to the Seattle Public Library, enter on 4th, take elevator or escalator up, and exit on 5th. Cross 5th and enter the U.S. Courthouse, take another elevator, and exit the Courthouse's 6th Avenue exit. All those elevators and escalators cut about 200 feet of climbing out of your walk up to 6th Avenue.
(Note: that route worked in the '90s. Some of those buildings have changed since then, so I don't know if there is an equivalent route now).