Taken from the GMod Tower website:
GMod Tower is a project comprised of many different unique gamemodes hoping to build a diverse community.
Essentially, the server (or tower) acts as a base for all the gamemodes it contains. You are not limited to one type of gameplay. The community forms what makes the tower interesting and the community controls how it's ran.
In the tower, you will have access to personal suites, stores, a whole batch of unique gamemodes, and much more.
There are plenty of well-thoughtout features/systems for your convenience. Trading (including currency exchange), grouping, gamemode queuing, awards (similar to achievements), and hand-picked administrators, just to name a few.
The various gamemodes on the server cane be found
here.To join the server, you will need to download the GMod Tower Updater, which can be found
here.Some of the various things you can do in GMod Tower (also taken from their website):
Play Gamemodes
PVP
Ballrace
Virus
UCH (Ultimate Chimera Hunt)
Zombie Massacre
And many more to come!
Watch Youtube (Either in the Theater, or in the Suites)
Listen to the Radio
Play Trivia, Tetris, Tic-Tac-Toe and a range of Arcade Games
Buy items for your suite
Buy player models, jetpacks, body manipulating potions, and other personal items!
Get a drink from the bar (and get drunk)
Earn achievements and milestones
Play different instruments such as a piano
Play lobby minigames
Snowball Battle
Chainsaw Battle
Plane Battle
Obama Smash
Balloon Pop
Take part in events such as
Cartoon Cartoon Fridays
Movie Night
And more!
Also, keep in mind this server was originally intended for Gmod 12, and there are many bugs and errors due to the Gmod 13 upfate, but they will be fixed eventually. Also, new gamemodes, furniture, items, and other content are constantly being added.
So if you ever get tired of RP and TTT servers, try out Gmod Tower sometime.