I was recently lucky enough to visit Southeast Asia, traveling through both Vietnam and Cambodia.
One of the most memorable parts of my trip, and indeed my life, was an excursion to the Cu Chi Tunnels near Ho Chi Minh City in the south of Vietnam.
The tunnel network were started in the 1940s as communist forces faced off against French colonial troops in the first Indochina War. They provided a subterranean world from which the Vietnamese guerilla fighters - the Viet Cong - could launch attacks and hideout.
With the onset of the war against the US in the 1960s — which ended up claiming the lives of over 58,000 US soldiers — the Viet Cong gradually began to expand the tunnel network.
The tunnels "provided the Viet Cong with manufacturing, resupply, and planning space within easy striking distance of their targets," according to The National Museum of the United States Army.
As bombing raids and smoke tactics failed to prevent the threat posed by the tunnels, the US began sending soldiers, who became known as "tunnel rats," into the tunnels to clear them.
Inside, the tunnel rats faced danger at every corner, and they had to watch out for ambushes, booby traps, venomous snakes, scorpions, spiders, bats, and mosquitoes, among other things.
Take a look inside the stifling tunnels, one of the Vietnam War's best-preserved relics.