The Israeli Defense Forces have discovered a vast network of underground tunnels in Gaza, known as the "Gaza metro," used by Hamas for smuggling, transportation, storage, and command centers. Hamas claims to have built 500 kilometers of tunnels, potentially half the length of the New York City subway system. The tunnel network is extensive and expensive to construct, with the exact cost unknown. Gaza has been under blockade since 2007, and experts believe Hamas used basic tools to dig the tunnels. Israel accuses Hamas of diverting resources from civilian purposes towards tunnel construction.