The caves could have sheltered as many as 500 fighters from air attacks
Colombian soldiers says they have found extensive caves deep in the country's jungle used by Farc guerrillas.
Special forces came across the caves after a five-year-long hunt for the secret hideout of a top Farc commander.
The caves, in Meta province, are thought to have been able to shelter as many as 500 fighters from air attacks.
Farc (Revolutionary Armed Forces of Colombia) is a left-wing group which has been fighting the government since the 1960s.
As well as protecting Farc's fighters from Colombia's air force, the caves south of the capital Bogota also included a bomb-making factory and thousands of kilos of explosives, mortar shells and mines, officials said.
Colombia's defence minister Juan Manuel Santos said one of the caves even housed an operating theatre and equipment to perform dental surgery.
They used to live like princes, and now literally they are living like rats
Defence Minister Juan Manuel Santos
"This proves that the wounded, including the leaders of the Farc's Eastern Bloc may have recovered here from their wounds and were sent back into combat. They used to live like princes and now they literally live like rats."
The BBC's Greg Morsbach says the subterranean medical facilities in Colombia are reminiscent of those used during the Vietnam War by the Communist Viet Cong fighters.
Special forces entered the network of tunnels and caverns after an intelligence tip off by a Farc deserter, our correspondent says.
One of the Colombian soldiers who found the tunnels, Yesid Arroyo, explained how they made the discovery.
"The dog traced the smell of explosives from the tanks they were in. Then we were led to here, and we found the explosives in a hole nearby.
"These are caves which they used to hide from us, but fortunately, because of our strength and the strength of all the Colombian people, here we are, and we have found them," he added.
Farc has funded its 44-year war against the Colombian government with drug-trafficking, kidnapping and extortion.
But under Colombia's new president, Alvaro Uribe, the military has launched operation deep into Farc-held rural areas, lessening the group's ability to launch attacks on urban areas.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.