That and the sewage treatment plant that the Japanese built. But I still like the way the Egypts handled their end of the tunnels: They started dumping their septic tank waste down them. Haven’t heard lately if they’ve kept up the program but there’s certainly enough poo in Egypt to plug plug a tunnel. At one point the Israelis had a plan to dig a sea level trench around part of the Gaza border but I suppose that would have actually cleaned the place up a bit.
Using ground sonar, find the tunnels,
add an aliquot of something flammable,
ignite,
wait for kaboom of stored munitions under Gaza.