At one time the tunnels had served as burial grounds for overflow from the cemeteries.

The tunnel has been constructed by intelligent beings and serves a certain purpose.

Some scientists believe these tunnels may serve as conduits for some plant roots.

The tunnel then served as a mushroom farm and ammunition storage facility during the war years.

Rumors have it that these tunnels serve clandestine functions in addition to flood control.

The tunnels may also have served for water supply and safe passage during siege.

In case of war, the underground tunnels could serve as a bomb shelter for the citizens of Moscow.

This tunnel serves to avoid a hill and contains no underground stations.

Also, tunnels can serve as the shelter of its troops and people from enemy attacks.

Built at a cost of $200 million, the tunnel has served no more purpose since then than a plundered Egyptian tomb.