The key there is a system of trap-doors and tunnels.
Nahr alBared, Lebanon
Among the emergency relief workers, the humanitarian workers, and medics flooding the strip, there will be some unexpected people trawling through the rubble before reconstruction starts.
A small army of architects and urban planners working with the Israeli human rights group B'Tselem, are poised to make a bee-line to the half-standing buildings that remain in the strip. In the broken remnants of Gaza, they say, lie the clues as to what shape Israeli military practice is likely to take in the future.
One of the few tactical advantages Palestinian militants have in the face of Israel's military might is an intimate knowledge and command of their own architecture and urban space. The maze-like streets, alleys, and thickly packed, high-rise buildings of the Palestinian refugee camps have played to the favor of militants in the camps in times of conflict.
This was made clear most recently in in 2007, when a small group of Islamic militants infiltrated the Nahr al-Bared Palestinian refugee camp in northern Lebanon and used it as a base. Holed up there, the militants manipulated the architecture to their military advantage, much as Palestinian militants traditionally have. The Lebanese military was unable to negotiate the camp and it took more than three months of heavy shelling to topple the militant group that was estimated to number under 1,000.