Tunnels under the DMZ

[MGH & HJM <bailey@e-scape.net>]

In the after word of Bevin Alexander's KOREA: The First War We Lost, 
Alexander talks about visiting a modern, bustling Seoul and later at the
DNZ is shown one of several tunnels that bisects North Korean tunnels that
were dug some 300 to 400 feet below the surface. These tunnels were used
for spy infiltration and, if necessary, troops.

Has anyone else heard of or have seen these tunnels first hand? Is it possible to view them?

Thanks

HJM