Underground base

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An underground base is a subterranean facility used for military or scientific purposes.

Examples are:

• Cheyenne Mountain Complex
• Chiashan Air Force Base
• Iranian underground missile bases
• Raven Rock Mountain Complex
• Zeljava Air Base

There may be more than 10,000 underground military facilities worldwide.{{cite web |last1=Richelson |first1=Jeffrey T. |title=U.S. Intelligence: Hiding of Military Assets by "Rogue Nations" and Other States a Major Security Challenge for 21st Century |url=https://nsarchive2.gwu.edu/NSAEBB/NSAEBB439/ |website=gwu.edu |publisher=George Washington University |access-date=16 July 2020}}