Despite being just a short drive from Split, the hilltop town of Imotski is hidden from Croatia’s well-beaten tourist trail.
Pulling in visitors are the nearby Blue and Red Lakes — or Modro Jezero and Crveno Jezero in Croatian. Just south-west of the Bosnian border, both lakes lie in deep sinkholes formed after the collapse of large caves in centuries past.
Water levels fluctuate depending on the time of year, but both are worth the hike for tourists and locals, who come to sit, swim, or admire the view.
But once every few years, the Blue Lake reveals its true colours, with waters that shine with the striking cerulean hue that gives the landmark its name.
It takes place thanks to an abundance of rain, which causes a sudden outpouring of water from the underground springs which feed the lake.
The transformation was caught on camera by local photographer Boško Ćosić.
The colour change isn’t the only reason that Blue Lake remains so special. The lake has also been known to disappear entirely during periods of drought — leaving locals to play football in its dried-out basin.