|Doom Wad Station
Boomtown is a 32-level megawad created by Scott Bardy (Birdman) and first released in November 1999, with subsequent updates being released in February 2000, July 2003, and April 2006. Boomtown is primarily meant as a deathmatch wad, but does include monsters for single player or coop play. A good number of these use sprites from Heretic and Hexen enemies (and even trees), but with the original Doom behavior.
It is noteworthy for its very large levels set in towns and castles, and also for being one of the first large scale projects to utilize the features of the ZDoom engine, such as deep water effects, scrolling skies and ambient sounds.
An update and follow-up to Boomtown called Lost in Time, meant to have more of a single player approach, remains unfinished to date, with some beta versions released.