By Henry Mance
La Macarena, Meta province
The region has long been off the tourist track because of security concerns
Residents of the town of La Macarena frequently toss a phrase into conversation: "Cuando estaba la guerrilla..." - "When the guerrillas were here..."
It is an understated way of describing the region's past troubles.
Between 1998 and 2001, La Macarena, together with four other municipalities, formed part of the demilitarised zone created by the Colombian government during peace talks with the country's biggest rebel group, the Revolutionary Armed Forces of Colombia (Farc).
Cano Cristales is famous for its pink-tinged waters
The guerrillas were not just a presence; they, and the drugs economy they brought with them, dominated the lives of the local population.
Farmers and merchants experienced an unprecedented boom from coca production.
Food crops virtually disappeared and plantains and cassavas had to be imported.
Meanwhile, instead of state law enforcement, there was a guerrilla-run complaints office.
Men caught stealing chickens and other items were ordered to walk around the town with sandwich-boards announcing their crimes; other offenders were taken off to work clearing runways for drug trafficking.
The broader conflict's victims were visible: a group of hostages was kept in a barbed-wire enclosure before being handed over to relatives.
At that time eco-tourism was impossible. But after peace talks between the government and the Farc broke down and the army retook the town within a week, the idea took root.
This year has been the busiest since the guerrillas left, with around 200 tourists from Colombia, North America and Europe flying in on tiny aircraft.
"I've wanted to come for years, but the trips were always cancelled for security reasons," says one visitor from Bogota.
The region's main attraction is Cano Cristales, a river famed for its pink plants.
It came to wider notice across Colombia in the 1980s when the explorer Andres Hurtado wrote about it, describing it as "the most beautiful river in the world".
Security concerns are still evident in the region
Now one of Mr Hurtado's pupils, Carlos Avellaneda, has led the way in developing the area as a tourist destination.
"The first thing that tourists come for is the red colour, which is rare in nature," he says.
"And they all agree that the photos don't do it justice, that it's much better to actually be there with the river next to you."
One ardent supporter of eco-tourism is Armando Cubides, who runs a local campsite.
"Coca brought only short-term benefits. When the guerrillas were here, there was no development. They built roads, but only exit routes for themselves," says Mr Cubides.
His wife recalls how, elated in the days after the Farc left the area, she drew the word "libertad" (freedom) on the sandy bank of a nearby stream.
In fact, one of the roads built by the Farc to transport drugs is now used to take visitors to Cano Cristales.
Yet in other ways La Macarena's history of guerrilla control and general isolation has been less favourable to tourism.
There was little knowledge about how to cater to visitors, along with an ingrained suspicion of their motives.
Mr Avellaneda says: "At the beginning, the locals fought between themselves [for control of the business], but now they've realised it's better to join together.
"They've made a lot of progress in understanding what tourists need."
Mr Cubides agrees: "People are becoming aware that this is good for a lot of us - those working in transport, hotels, restaurants, growing food."
The modest success of this year's tourism led environmental authorities to open parts of the nearby La Macarena National Park that had been off-limits because of security concerns to visitors on 10 September for a 60-day trial.
The exceptional biodiversity of this corner of the Orinoco basin means that a limit will be put on visitor numbers.
"We've been looking at other experiences [of tourism in Colombia], but this is a very fragile and special area. It has savannah, forest and other ecosystems, and that makes managing the area more difficult," says Fernando Sacristan, co-ordinator of the environmental authority, Cormacarena.
Continued guerrilla presence in the area means that the park must first be secured by the army before visitors arrive.
Soldiers are seen as increasingly friendly towards civilians in the area, although Mr Sacristan says that troops have little environmental awareness.
"They leave all the litter and create all the impacts that you'd expect from 200 people."
Despite these concerns, Mr Sacristan believes there is currently a balance between conservation and the needs of local communities for income.
For the government of President Alvaro Uribe, being able to open some areas of the national park - even if other parts are still home to coca crops and illegal logging - is a minor political coup.
Developing tourism could be a way of boosting the local economy
The area around La Macarena is the testing point for what is known as its strategy of integral development, which seeks to combine military presence and social projects.
On a visit to La Macarena in August, Mr Uribe celebrated government spending of some $104m (£65m) in the region.
But the lingering sense of insecurity does hamper tourism.
Paradoxically, many Colombians, keen that foreigners should visit the country, are themselves reluctant to visit Cano Cristales.
News about the La Macarena region usually focuses on the army's hunt for Jorge Briceno, alias Mono Jojoy, the Farc's military leader.
"They hear about violence in La Macarena Park and they think it's here. They don't realise that it's a huge area," complains one local.
At the same time, Mr Avellaneda knows the risks if the Farc do stray closer to Cano Cristales.
"If a guerrilla is so much as seen in the area, it will destroy the business," he says.