A.R.K. has built in requisitions, R+D Lab, armory, vehicle bay, VR training room, command bay, Persephone's office and a lounge.
Armory is ran by Claymore. The armory is used to equip Gadgets, Upgrades and Tech that you can build at the R+D Lab or earn through the progression of the game.
For more information on gadgets, see Gadgets.
Wreck room is ran by Mixer. In here, agents can complete various VR Training Programs to test out the gear, agents or simply complete the challenges.
For more information on the VR Training Programs, see list of Training Programs.
Requisitions is ran by Relic. In an exchange for cash, Agents can buy unique Agency Upgrades. This room can be used to perform a glitch that allows the player to get inside of the normally unaccessible vehicle room and get outside the A.R.K. interior. Sadly the town has no collision and jumping down from the interior will cause the player to fall through the map and respawn back inside the A.R.K. This glitch can be seen on this video (exact tips can be found in the description).
For more information on agency upgrades, see Agency Upgrades.
For more information on upgrades, see Agency Vehicle.