Little attempt is made to keep them secret. They are surrounded by huge mounds of sandy earth which have been dug out of the ground.
The air is thick with diesel fuel from the trucks that transport the goods across the Gaza strip.
The openness of the smuggling operation suggests that if Israel and Egypt really wanted to stop the tunnels they could easily do so.
Israel has at times bombed some of the tunnels, but has stopped short of totally shutting them down.
Aid agencies in Gaza say that if Israel or Egypt really forced the smuggling to stop, it would lead to an even more desperate humanitarian situation in Gaza which would be damaging to Israel's and Egypt's international reputations.
Diplomats in the region also believe that so much money is being made in Egypt from the trade through the tunnels that much of the smuggling is likely to continue.
But the head of operations in Gaza for the UN relief agency Unrwa, John Ging, says that ordinary people in Gaza are losing out.
"Everything is expensive because people are hostage to the dynamics of a black market."
Mr Ging stressed that it was the Israeli-Egyptian blockade that was allowing that black market to thrive.
The UN does not use illegal goods and building materials smuggled in through from Egypt.
If the blockade remains in place it seems the tunnel industry will continue to thrive, underground steel barrier or not.
"If they opened the border, we wouldn't need to dig tunnels," says Mohammed peering into the shaft of his tunnel in Rafah. "But until they do, we'll keep digging, whatever they do to try and stop us."
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