Tunnels are some of the greatest engineering feats humanity has ever undertaken. We (humankind) have, in fact, been digging them for millennia.
But, they have not all been excavated for purely logistical reasons. Tunnels were, and still are, widely used for mining operations and were commonly used in warfare.  
Predecessors of modern tunnels were called adits that were built to transport water for irrigation or drinking and sewerage. The first Qanats, early underground aqueducts, have been from well before 2000 B.C.

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