GMod Tower was a unique community-based lobby with centralized multiplayer games. It was a modification within Valve's Source Engine.

GMod Tower was a collection of various online multiplayer games that each have different genres of gameplay. Each game could be played with 4-90 players across the globe and are complete modifications of the Source engine.

The lobby aspect is what made it all work. Players connected to a central lobby server and group up with other players to play these multiplayer games. While in the lobby, they could also watch Youtube together, buy furniture and items (such as a piano) for their in-game house, customize their look (hats, skins, etc), bet on casino and cards games, play trivia and arcade games, and participate and various daily activities.

GMod Tower started in late December 2006 as one of the most ambitious ideas to come to the Source engine. It later went through three different sets of development cycles/teams until finally becoming to fruition by a handful of just four.

The four man team was comprised of MacDGuy, Mr. Sunabouzu, Nican, and AzuiSleet. Development of the GMT you knew and loved was done from early October 2008 until its first public release on July 2009.

The release was an incredible success. From all across the globe, GMod players battled to join and play GMod Tower upon its first two launch weeks. In just a couple hours after the release, our website hit a total of 2 million unique hits and our server was getting queried by 30,000 unique GMod players. It was one of the most talked about and impressive launch. Our release even made Garry up the server player limit from 64 to 128.

After the release, things were a little more calmer than that, but popularity of the mod was still very strong. In fact in total we had around 48,000 unique GMT users.

GMod Tower grew, adding new gamemodes, tons of new items, and lots of fun. GMod Tower lasted a full 2 years before temporarily shutting down on 1/1/2012.

On April 17, 2012, the servers were officially announced to come back with new updates to the content, look, and gameplay, and a complete rewrite of the code, and a new gamemode: Zombie Massacre.

In 2013, Minigolf and Source Karts was added as new gamemodes.

On September 12, 2014, Lobby 2 was announced.

On Feburary 6, 2015, Lobby 2 was released.

GMod Tower closed down permanently on April 8, 2016 to be reborn as a standalone project titled Tower Unite.