[Updated] What is that atop the Jefferson?

We were walking east on East 13th Street Friday afternoon (oh, how was your weekend?) and we spotted this atop The Jefferson, the incoming condo ...



That.



What the hell is that?



Don't recall seeing that in the renderings.

Shared building amenities include a rooftop terrace with party facilities and a BBQ. Maybe it's a party facility? DJ Booth? Portal to the 18th century?

Guesses as to what this is... are welcome in the comments.

Updated 10:20

Curbed quickly cleared up the mystery, looking at some zoning diagrams and noting that this is an "allowable rooftop obstruction" for an elevator machine room. That's boring!

Previously on EV Grieve:
City approves new building for Mystery Lot

The last days of the Mystery Lot

Before it was the Mystery Lot

The Mystery Lot developers using famous dead comedians to sell condos at The Jefferson