|A Gaza tunnel (Time)|
"Gaza’s underground: A vast tunnel network that empowers Hamas (Al Jazeera)"
"Israel Surprised by Number, Sophistication of Gaza Tunnels" (Fox News)
and given that Al Jazeera and Fox News don't often agree, even on the time of day, I suspect some fellow geezers of my generation will immediately think "Cu Chi."
During the Vietnam War, the National Liberation Front (Viet Cong) had a 75-mile long underground network of tunnels in the Cu Chi district outside Saigon; these contained command posts,and other facilities and provided an operational center for the Tet Offensive of 1968. Today the Cu Chi tunnels are a Vietnamese War Memorial, with tours available.