[Mr Downtown]

^The "Suburban Concourse" has been closed on Sundays for decades. I'm not sure why, but there are restrooms and benches down there, so may just be a security personnel issue. Typically the stairs down from the platforms are chained off late nights and Sundays, as it's obviously dangerous to have people descending into what they think is an exit only to find it locked. I suspect at least one door in each set has a panic bar, though it may be alarmed.

The entrance from Washington near Canal is open whenever the building is open, so you could have avoided a block of rain that way.