Hi! Let's do some dungeon delving. (I probably should have ported these sets along with Underground Castle, but I'm too lazy, sorry)
The Underground Tunnels is a Third Encounter mapset by Dustin Hein, 10 maps in total. Early maps feature some open areas and big rooms, but the set evolves towards narrow, winding passages with enemies lying in ambush over time. Generally interesting and worth a go.
The Underworld!!! is a First Encounter mapset by an unknown author, 10 maps in total. Most maps are very small and short, or large but still short, the only exceptions being the final two floors, which are both large and long (and harrowing). Generally interesting and worth a go.
Wolfenstein Underground is a First Encounter mapset by Yohei Sasaki, 10 maps in total. These maps feature a variety of combat scenarios, including at least one huge maze. A lot of backtracking is often invovled, which is rather unfortunate. Still, generally interesting and worth a go.
Excellent mod Continue, it's excellent. (join us, fbd)