Please help me identify this level

I've been searching through megawad after megawad in order to find it again but all to no avail. I remember it is definitely part of a megawad. I'll give as much detail as I can and hope it rings a bell with someone. (I last played it some years back so this isn't a recent creation.)

The first thing that is striking about the level is the number of yellow doors. While first exploring the map it seems that every direction you go in your path is blocked by a yellow door (there must be at least six or seven) and no progress can be made until you find the yellow key.

You start off in a very shallow depression which opens into a circular arena open to the sky. You are surrounded by very high elevators (open style with no doors), around six of them, I think. These lead to other areas among which are:

a courtyard with blue armor on an initially unreachable platform
a large spiraling staircase
a long high walkway with hostiles attacking from behind bars on each side (a switch on one or two of the sides needs to be shot to open the door at the end)

I do recall other details but not with as much confidence so I'll just hope that there's enough here for someone to remember the map. I'd love to play it again.

Can you estimate what year it was made in? You can usually tell by the level of detail. Given the complexity of it I'd guess it's somewhat of a 1996 or 1997 wad

Also, what texture themes? Kinda...important.

Textures were pretty much standard Doom 2 as I remember, maybe some TNT.

They meant something like, tech base, hell, rock...