At first glance - Gaza's southern border is a wasteland, battle-scarred, patrolled by Hamas and separated from Egypt by a wall.
But a set of derelict buildings shown on CBS News video hide a secret that CBS News correspondent Elizabeth Palmer found her way into.
It's a subterranean maze that makes a mockery of Israel's efforts to seal Gaza.
Veteran smugglers took CBS News down for an exclusive look.
One tunnel goes straight under the desert about 40 yards and comes up again in Egypt. Its part of a whole labyrinth of tunnels here and it's the mainline smuggling route for everything from explosives and people to cigarettes.
One Palmer saw was only about two feet in diameter, but it's a lifeline for the million and a half residents of Gaza, who struggle to get basic supplies now that Israel has closed the roads.
How long did it take to make the tunnel?
"From here down and all the way out," a smuggler said. "Three months."
Who paid the smugglers to do it?
"Somebody paid us to dig it," he said. "Then once it started working, we got a cut of the profit from all the goods we brought it."
United Nations staff estimate that 10 percent of goods coming into Gaza are smuggled through the tunnels, including life-saving medicine … at least - explains one pharmacist - for those who can afford contraband prices.
Palmer asked one resident: "So now that the borders are closed, how do you get the drugs you need?"
"Through the tunnels," the resident said. "People can get what they need, but it's very expensive."
But it's not drugs - or cigarettes - that Israel's worried about, it's the security risk.
Last year, Hamas tunneled into Israel and kidnapped a soldier - Gilad Shalit - who, eighteen months later, is still a hostage.
In that time, the Israelis have blown up over 30 tunnels, but - says Israeli intelligence - there are plenty more.
Funneling the weapons, explosives and Iranian cash that Hamas needs to crush all opposition in Gaza.