Research Hangar

The Research Hangar is the first map of Unit 3 of Quake II Mission Pack: Ground Zero. The level begins the moment you left Base Complex via overflow tunnel and you found yourself in a secret research hangar complex surrounded by a lava.

A section of the facility (when you pick up an airstrike marker guarded by a Gladiator) has been ruined due to the crash landing of a Drop Pod called Zor; an Easter Egg was referred to Rogue Entertainment's level designer (of that time), Berenger "Zor" Fish. "Zor" is also referenced during the introductory cutscene.

Walkthrough
Your aim is clear - destroy Anti-Aircraft Gun and for that you will need to reprogram the Gun and call an airstrike. Proceed through a facility eliminating the resistance until you pick up an airstrike marker guarded by a Gladiator. Then take it to the AA-Turret, place it nearby and reprogram AA-Gun so that an airstrike will succeed. After you destroy the gun, make your way to the other side of the canyon, where is the hangar. Unfortunately the bridge equipment is malfunctioning, which means you will have to find an alternate way through a broken pipeline in the canyon and get to the next level - Waste Processing.
 * Research Hangar for the first time:

At last you found yourself in a hangar itself. Now the only thing you have to do is to secure the Strogg Prototype Fighter, and because of that you will have to face a first boss you encounter in Ground Zero - the Carrier, which patiently waited for you to attack. Once you defeat an enemy proceed towards Munitions Plant using underground train.
 * Research Hangar for the second time (after coming back from Maintenance Hangars):

Secrets:

 * #1) In the second big room of the map, you will see a suit of Body Armor located in an elevated alcove, blocked by a red laser beam. Face the highest point of the walkway that loops around this room, and look up; there is a Shootable Button located on the ceiling, between the leftmost column and the wall. Shooting it will cause a chain reaction, culminating in the lower level getting flooded. When the water level reaches its highest, the red laser will be disabled, allowing you to retrieve the Body Armor. There is a non-Secret Adrenaline that you can now get as well, inside the pipe on the lower level that was destroyed in the chain reaction.
 * #2) SECOND VISIT: When you enter the final room before the Carrier boss fight, look at the computer servers in front of you; the tallest one contains a secret item. Jump to the top of the shorter servers, and then shoot the top of tallest one until it explodes to reveal a Power Shield.