BBC News | In Depth | War on terror

The search for Osama Bin Laden is focusing on a few key areas of Afghanistan where it is believed that both the Taleban and the al-Qaeda organisation have developed cave and tunnel complexes. These areas are thought to be near Kandahar and Tora Bora in the border region of Nangarhar.
Many of these systems are hundreds of years old. Some may be left over from the Cold War when the CIA secretly trained and armed anti-Soviet Mujahideen. Few people outside of Afghanistan have ever seen these systems, but they are thought to be fortified and possibly large enough to hide large groups of fighters.

Click on the numbers to find out what the US is looking for.

		1. The caves and tunnels The search for Osama Bin Laden is focusing on a few key areas of Afghanistan where it is believed that both the Taleban and the al-Qaeda organisation have developed cave and tunnel complexes. These areas are thought to be near Kandahar and Tora Bora in the border region of Nangarhar. Many of these systems are hundreds of years old. Some may be left over from the Cold War when the CIA secretly trained and armed anti-Soviet Mujahideen. Few people outside of Afghanistan have ever seen these systems, but they are thought to be fortified and possibly large enough to hide large groups of fighters. Click on the numbers to find out what the US is looking for. See also: Bin Laden's fortress caves