Base

1. A fortified center of operations. After D-Day the forward base was in Normandy.
2. A supply center for a large force of military personnel. My basic training was the base at Fort Ord in California.
3. The lowest or bottom part. The car ended up at the base of the cliff.
4. The supporting part or layer; a foundation. The tall building sat on a base of solid rock.
5. A place of concentrated activity, influence, or importance. The base or the NBC network is in New York.