A quite nice map, with great connectivity and some memorable but distinct scenes!
It also uses height variation and walkways over and around liquid to great effect in order to impressively attain a coherent sense of place without using any outdoor areas whatsoever. In fact, I would argue that the lack of outdoors is a big part of what gives this map its atmosphere. I forget if there were any sky sectors in it, but the map feels like it could easily be underground or built into the side of a cliff or something...
The one thing that keeps me from finding it completely authentic, I think, is that some sections (particularly the central main hall near the start, that you revisit a bunch of times) feel somewhat overly tightly packed-together, with some walls and shapes seeming unnaturally crampy as a result. I think probably the easiest example of what I mean is the two windows into different heights placed really close together near one of the yellow key doors, visible from (322,-508). On a related note, I'd also undo some of the startan alignment; that window area and a couple of others feel autoalignish.
I also have to wonder how much better this already great map could be with more texturing variation. Right now it's almost entirely STARTAN3, which combined with the gray stone floors and a few other elements make it feel very reminiscent of E1M7, but I don't think the map structure itself is homagey at all. I'd consider switching up the main theme somewhat (though I realize it can be rather difficult to find an e1-authentic texture/flat combination that doesn't immediately look like an existing e1 map), and also incorporating a couple of different textures into some scenes in place of some of the startan.
Anyhow, these are all rather minor and easily corrected issues in a map that I think absolutely deserves a lot in episode 1.