The Archiech Bunker is a bunker for the Architechs. It was built in Grian's Season 6: Episode 94.
The location of the bunker is underneath the diamond pile at the front of the Sahara lobby. For a while, the entrance into the bunker was just a hole in the ground, until Iskall85 built a secret redstone entrance for it in his Season 6 Episode 158.
Inside the Bunker
The bunker is split into two rooms. The first room contains two beacons, which were rigged up by Iskall to turn on at the push of a 'Panic!' Button.
The second room has been terraformed to look like a cave. It also has a dragon head build that leads to the secret Dragon Bros meeting room. It contains a tunnel, leading to Mumbo's Bunker. The dragon heads' insides were blown up in Demise, killing Grian in the process.