Tunnel warfare in the Gaza Strip

A vast network of underground tunnels used for warfare and to avoid Israeli airstrikes exists in the Gaza Strip. This infrastructure runs throughout the Gaza Strip and towards Egypt and Israel, and has been developed by Hamas and other Palestinian military organizations to facilitate the storing and shielding of weapons; the gathering and moving of fighters, including for training and communication purposes; the launching of offensive attacks against Israel; and the transportation of Israeli hostages.

Source: Wikipedia — Tunnel warfare in the Gaza Strip (CC BY-SA 4.0)