Perched amid high mountains, Kooh Lake ─ a 'colour-changing' glacial lake in Anakar, Kalam valley ─ stands out from the 50 other such lakes spread over the alpine zone of Swat valley.

The lake, popular for its pristine water, is located 10,800 feet above sea level and can be reached after a seven- to eight-hour-long trek that guides visitors through a beautiful, lush-green valley.

It has nonetheless become a wildly popular attraction for local tourists and adventure seekers.

Tourists are mesmerised by the lake as they catch its water suddenly change colour: from blue, to green, to crystal clear.

“This lake is different from other lakes in Swat due to its unique colours, which attracts visitors and leaves them in awe," Azhar Uddin, a professor in Swat University and a trekker who visited the lake with his friends, told Dawn.

"From above, the lake looks blue, whereas from the edge of the lake, its waters appear to look emerald green. From some angles, however, the water is crystal clear,” Azhar adds.

Faisal Murad, a trekker who recently visited the lake with a group, said they had set off on a trek to the lake early in the morning after spending a night at Anakar valley.

“The trek is not very steep or difficult, as it runs along a stream coming down from the lake. We set up our camp at the Maidan pasture after a seven-hour trek and spent the night there. Early next morning, we reached the lake in one-and-half hours after a steep climb towards the end,” Murad told Dawn recalling his visit.

He said once they arrived at the lake, the group "felt at peace".

“It is amazing and enchanting for its serenity and beauty. It gives respite from the busy and noisy daily life in the city. I feel relaxed here and it brings me peace of mind as there is no population, no noise and no stress,” Zafar Ali Kaka, another trekker, said, echoing Murad's experience as he relaxed near a tent at the Maidan pasture after visiting the lake.

“Nature is at its full bloom in the entire valley, right from Anakar to the lake, where one can enjoy the blue streams gushing passionately, the lush green pastures, the thick forests and the colourful small flowers that welcome visitors with their fragrance,” Ziaullah Khan, another visitor to the lake, said.

Tourists say that the lake and the valley are two of 'hidden gems' in Swat valley.