Yeah, that level uses Descent 3 textures. It's a D2X-XL level (i.e. it uses D2X-XL specific extensions on top of the standard D2 level format). If you would like to take a look at the entire level, you can find it on my web site: Chose "my missions - multiplayer" in the side scrolling menu at the left of the home page, then use the side scrolling menu at the destination page to quickly jump to a particular level.
TombZ of D3struction, Pyrotechnica (D3), Pyromaniac (D3), Styx (D3), Tank Boy, Glass House, Speed and Toxic Descent are other levels of that category.
There are other cool missions making use of D2X-XL extensions (you probably know them already), like Pumo's 3 level "Kartsal" demo where he virtually modded everything, Sirius "Anthology", Aus-RED-5's monsterball multiplayer level "Monsterball Arena" (D2X-XL has a monsterball game mode, too), and Yokelassence's "The Sphere" and "Dimensional Intersect". Wolfie has made a very cool 6 level multiplayer mission named "Chaos Theory XL" which I have refactored into D2X-XL levels using D3 textures.
You can find an up to date D2X-XL gameplay video showing many of these levels on Youtube