The Lost Mission gets a lot of flack for copy-pasting a lot in the UAC bases.
BUT, the Hell level was amazing. Actually, it is more dreadful and intense than the Hell maps in Doom3 and ROE.
So there's that. Thanks to the team who made The Lost Mission, there were great things in there.
I liked the way the Hell map in the Lost Mission had the bizzarre spiral-mountain-things and castles. The castles were awesome.
The interiors were especially terrifying.
I love the heavier use of screaming and weeping/moaning in places where we'd see blood streams and there was that crazy chamber with the blood pouring down all the windows.
There's a lot of crazy [censored] in there. It's easy to miss, but they paid attention to detail.