Threewave CTF for Deathmatch Classic (unreleased) - The Warzone (full level walkthrough)
The Warzone is a map for Deathmatch Classic's cancelled addon, Threewave Capture the Flag.
Threewave CTF itself is a port of the Threewave CTF mod for Quake to Deathmatch Classic that never came out, but was leaked in 2003 with the Half-Life 2 beta and other content from Valve.
This is a symmetrical CTF map that has each base look like a castle. In the center of the map is a house-like place with goodies, like a megahealth, inside it. There's a bunker in front of each one for defenders. An alternate path to the megehealth house can be found in each base, but the grappling hook or rocket jumping are required to reach them.
The Warzone is one of two maps in Threewave CTF to have the biosuit, an unused item in DMC, but it doesn't work. That's sort of a problem, as the water routes to each team's base are long enough that you'll start drowning.