[StClaire]

Denver has these, you can see them on Larimer and Market street in LoDo. Around the 1890s, the locals dug out a series of tunnels through the city. The snows would come in and people would just go underground for a few days for business. There was a bar that closed about a year ago called the Blake Street Vault—it used to be a bank—and if you asked they would take you into the basement to see the vault and the dumbwaiter. You can see down where they plastered over some of the wall, it used to have a teller window right there open to the tunnels for customers.

Supposedly, you could go from Union Station all the way to the capital building underground (but I doubt that).

I’m sure most of the tunnels aren’t passable, possibly collapsed, filled in, or flooded. But I seriously want to go down and try to map out some of them to be restored like they did in Seattle.

[lozaning]

I've got some friends in Minneapolis that November - ~May don't leave the skyway system. Seems similar, but connects buildings at the 2nd story instead of underground.

http://www.skywaymyway.com/

[brodie78382]

We have these old glass grids in the sidewalks along College Ave up here in Fort Collins as well. Some are even still in use by restaurants to load inventory from the Cysco / Shamrock trucks.

[rconti]

Stupid question: Wouldn't the snow cover the vault lights? (I know, they could clear them by clearing the sidewalks...)

[sampo]

Snow also scatters light a lot, if it's not too dirty. One example I found, it takes about 8 cm (3 inches) of snow to reduce the light irradiance to half.

[jrace]

It would. But not 100%. Same with skylights, depending on the depth and density some sunlight still makes it

[jrochkind1]

They weren't clearing the sidewalks to let light through, they were (and we are) clearing the sidewalks so that people could walk on them! Anyway, with or without prism tiles.