What is this?

[glatt]

I'm changing my answer. Looking at the picture again this morning, there's clearly no glass there. What I thought was the edge of glass is actually a bit of flashing wrapped around the beams.

This is a concrete post with staggered beams going off to the sides of it. We're looking up toward the sky through the beams. I figured it was some sort of ramp in a parking garage. Then I saw you had been to Sitka. So you must have gone to an airport. I looked for instances of Seattle airport parking garage ramps, and found somebody somewhere commenting on crazy ramps at SeaTac.

So that's what this is. One of the spiral ramps at SeaTac airport in Seattle.