If you want to play some of the custom maps, you will need to download some of our maps. Get them here: http://hidden.wallworm.com/wwhidden.zip. Extract the contents into your Hidden installation folder.
The maps currently include hdn_sacrelige_beta4 by Wall Worm owner Shawn Olson. That map hasn't been updated in a couple years but Shawn is working on an updated version for both CS: Source & Hidden: Source. The other two maps in the download include hdn_kindergarten and hdn_eminence.
Newer versions of Hidden/Steam have turned off the automatic ability to download custom maps in Hidden (and possibly even made the solution listed here unusable.). Since the WallWorm server runs custom maps, you will have to turn this feature on if you want to play without getting kicked on change to a new map. The temporary solution is to go into the Console and type cl_allowdownload 1. That will allow Steam to download maps while you are connected. A more permanent solution is to edit your userconfig file to include that line. If this solution fails, you will have to download the file linked above to play here.
For those of you who have played on our server in the past, here are a few updates:
We stopped hosting a Hidden server for a year or so since many of the Wall Worm players moved back to CS:Source. We have recently put the server back online in preparation for beta 5 of hdn_sacrilege. In July 2010 we opened the server back up to the public.