By Matt Prodger
BBC correspondent in Podgorica
At a tiny hilltop cafe in northern Montenegro, a musician plays the gusle, a single-stringed instrument that has been part of the local culture for hundreds of years.
He's singing a love song for Tara... not a woman, but a river, Montenegro's most famous in fact.
The Tara runs for more than 100km (60 miles) through one of the deepest, most secluded and beautiful canyons in the world.
The canyons and waterfalls are part of a world heritage site
The river is part of a Unesco world heritage site, but now a plan to build a hydroelectric dam on it has brought Montenegrins onto the streets.
Protesters say the Buk Bijela dam - a proposal to supply both Montenegro and neighbouring Bosnia with electricity - will swamp a large part of the Tara, turning it from river to lake.
Environmentalist Milos Stanic, who has lived beside the Tara all his life, says the valley "is supposed to be sacrificed to solve Montenegro's energy problems".
"But that's nonsense," he says. "There are better solutions. The Tara is a gift which we need to protect for future generations.''
There is no doubt that Montenegro desperately needs more electricity. On the outskirts of the capital Podgorica is a vast, sprawling, aluminium plant. It uses up nearly half the country's electricity.
Economists say it is inefficient and should be closed down. But the government says it cannot afford to.
"What is most important is that the aluminium plant provides some 43% of the GDP in Montenegro," says Montenegro's Economics Minister Darko Uskokovic.
"It will be very difficult to shut down the aluminium plant, because then we have to shut down the bauxite mine, a significant number of jobs will be lost in the port, on the railroads, so it would be very bad for Montenegro.''
Mr Uskokovic says it is impossible to generate more electricity without some environmental impact, but that a hydro-electric dam is the best, and cleanest, solution.
It is not just local protesters who are worried that the waterfalls cascading into the Tara could soon be silenced.
Unesco is as well. Its representative in Montenegro, Garrett Tankosic Kelly, says the national park could end up on Unesco's red list of endangered sites.
"Unesco has opened a file on this which is being investigated by the head of their European office," he said. "A team will be sent here to do an investigation. The Durmitor site may be placed on a red list, which would be a significant outcome.''
The fast-flowing Tara could be brought to a halt by the dam
The Tara has some of the best whitewater rafting in the world, attracting tourists from across the Balkans and beyond.
But one of the fastest stretches of the river will be brought to a standstill by the Buk Bijela dam.
The government says it will be constructed outside the national park and that the environmental impact will be limited.
This is a country fiercely proud of its natural heritage. But it is also poor. It is a dilemma which few expect to be resolved without pain.