"We have visited Gaza tunnels dozens of times before – but only ever the ones linking the enclave to neighbouring Egypt and used to pass goods across the border," write AFP's Mahmoud Hams and Yahya Hassouna. "Today, we are going to get a glimpse of a world under Gaza and the fighters who dwell there. Those same fighters who vanished from view during last summer’s war. Islamic Jihad has agreed to take us down into the heart of its best-kept secret."