The armor base is the source of almost all tanks, some armoured recon and one case of armored anti-aircraft (Japan). This has an average price of $30 and is one of the most common bases.
This is one of the more high risk buildings because, if captured, it can turn out tanks fast enough to wipe out your HQ. Eliminating these when used as forward bases is key. It usually takes two medium bombers or four dive bombers to take this out.