One of the oldest Techno clubs in Berlin first opened in March 1991, excepting the small break for the move into a new building, is the Tresor Club. You can read the full history here: Here
I ended up here pretty often with my sister, of course in the cellar - the Tresor, which is to reach after following a long, dark underground corridor. I remember crazy parties down there when the music stopped, the lights went fully off and everything was quite for a couple of seconds.
Nobody moves, nobody panics either.
The long-drinks are pretty cheap and as well very high on alcohol, usually I'm fine with 2-3 for the whole night. Next to that the sound is usually very bass-intense and of great quality. The people, layout and pressure reminds me a lot of the illegal bunker parties happening in my hometown twice a year. (Not sure if they where or still are illegal tho)

Music: Techno / House / Experimental Electronic
Floors: 1-3
Outdoor Area: No
Crowd: 18+
Pricing: Pretty Cheap
Link: Tresor
One thing to mention is, of course, since the club is one of the oldest of it's kind