Red Lake

Red Lake (Crveno jezero) sits right on the edge of Imotski, in Croatia's Dalmatinska zagora region, just a short walk from the famous Blue Lake. It's one of the most dramatic karst landscapes in Europe — a giant sinkhole formed where the roof of an underground cave collapsed, leaving behind a sheer rock wall plunging hundreds of metres into dark water.

What makes it so unusual?

The total vertical drop from the rim to the bottom of the sinkhole is around 530 metres, while the water itself is estimated to be somewhere between 255 and nearly 290 metres deep, depending on the measurement method and season. Pinning down the exact figure took decades: cave divers first attempted it in the 1990s, and a remotely operated underwater vehicle finally delivered a confirmed reading in 2013. That makes Red Lake one of the deepest known bodies of water formed inside a collapse sinkhole anywhere in the world. The name comes from the reddish-brown colour of the surrounding cliffs, rich in iron oxide, which glows especially bright at sunset.

Unlike the neighbouring Blue Lake, which can dry up completely in summer, Red Lake never disappears — it's fed by an extensive network of underground karst channels and ranks among the largest natural groundwater reservoirs of its kind in the world. Researchers have also found previously undocumented species of cave fauna living in and around its waters.

How do you get there?

The lake sits right on the road connecting Imotski and Vrgorac, on the edge of the small settlement of Glavina Gornja, essentially at the town's doorstep. It's a few minutes' drive from central Imotski, and there's parking near the main viewpoint. Imotski itself is roughly an hour's drive from Split, or easily reached from Mostar in Bosnia and Herzegovina. Blue Lake lies just a few hundred metres away, so most visitors see both in a single afternoon.

What will you see?

The main draw is the view from the rim: vertical, rust-coloured cliffs drop for dozens of metres to a dark, intensely blue-green pool below. A walking path runs along the edge with several fenced viewpoints, offering panoramic views over the whole basin and the town of Imotski in the distance. The site is also popular with climbers and cave enthusiasts — the surrounding cliffs and caves have drawn karst researchers for decades. Local legend holds that nobody has ever managed to throw a stone all the way across to hit the far wall, and plenty of visitors still give it a try.

When should you visit?

Spring and early summer are the best times, when the surroundings are green and water levels are high. Summer can get hot and crowded, especially since it's paired with a Blue Lake visit — which is often dry by then. Autumn and winter bring a starker but quieter atmosphere; pack warm clothing, since the rim can get windy.

Frequently asked questions

Can you swim in the lake? Direct access to the water is very limited and dangerous due to the sheer cliffs — most visitors only view the lake from the upper viewpoints.

How much time should I set aside? Walking along the viewpoints takes about 30–45 minutes, but combined with the nearby Blue Lake, plan on 2–3 hours.

Does the lake really never dry up? Yes — unlike Blue Lake, Red Lake holds water year-round thanks to its connection to the underground karst system.

Is it safe for children? The viewpoints have railings, but the sinkhole's edges are steep, so children need constant supervision.