When you see this river you’ll think you’re staring at liquid sky. Perhaps the most famous river in Costa Rica, Rio Celeste is a turquoise blue wonder. The water gets it’s color, not from magic or the blood of smurfs, but actually a rather interesting physical phenomenon. Two streams come together and where they merge the water suddenly changes color to the bright turquoise that the river is famous for.

Although many will tell you it is a chemical reaction, in reality the splendor of Rio Celeste is an optical illusion known as Mie scattering. The river is located within the Tenorio Volcano national park, and as a result one of the two streams has it’s headwaters on the volcano’s slopes. As a result the water is slightly acidic (not nearly enough to be dangerous however). The other stream has a high concentration of aluminosilicates (minerals that combine aluminum, silicon, and oxygen). What happens is the slight acidity of the one river causes those minerals to clump together. This results in light being scattered when it hits the water, causing the colorful phenomenon.

The water does have a slight sulfur smell because of the nearby volcano, but it is no more harmful than swimming in any other river or stream. Now that we have the science out of the way let’s talk about the fun part–exploring the river!

Hiking along Rio Celeste has two entrances; one paid, one free (technically a voluntary donation). It used to be local secret that you could enter on the free side, hike to the end, and then cross over to the paid side without having to pay. The operators of the paid side have since gotten wise and now posted a guard at the point you can cross over. If you want a real hiking in the jungle feel, go for the free side. If you want maintained paths and viewing platforms go to the paid side. [Update: The National Park Service has closed this free entrance as of 2015, but has plans to re-open it as a paid entrance with trails in the future.]

Getting to Rio Celeste from La Fortuna involves heading north towards Nicaragua. About forty-five minutes from La Fortuna is the only large town on your way to Río Celeste called Guatuso (San Rafael de Guatuso on all the official signs, but just referred to as Guatuso by the locals). From there you will continue another fifteen minutes to the smaller town of Katira. Once you get into Katira there will be a Super Christian grocery store on the left and a soccer field on your right. From there you need to continue about 300 meters to the only paved road on your left. Once at the paved road continue straight for about half an hour until you arrive at the park entrance. There is one intersection on the route, but there are signs there to direct you to the entrance.

The entrance of the park is hard to miss with its large parking area and ample signage. You’ll want to arrive fairly early as the park only allows entrance until 2 PM. At the entrance there are bathrooms and a small ticket office. The cost of entrance is $12 for foreigners or 800 colones for Costa Rican nationals and residents.

Getting to the river requires hiking about 1.5 km before you really get any good views of the river. At that 1.5 km mark the trail will split with steps to your left descending to the 100 foot tall Waterfall and the trail to your right continuing another 3.5 km to where the water changes color. To hike the whole trail out and back takes about 2-3 hours. I highly recommend sticking with the trail all the way to the end “Tenorio I”/Teñideros on the park map. [Link goes to the park map/brochure].

It is not legal to swim in the park itself, and there are often guards posted to prevent it. The reason is not actually health related in the sense that the water is dangerous, the law was created after someone died by getting sucked under the waterfall and the force of the water broke their back. If you want to swim in the river just outside the park about 1 km down the road (heading back towards Katira) is a bridge where you can swim legally and enjoy taking pictures in the uniquely colored water.

On your hike you will also see many animals. I’ve seen monkeys, butterflies, birds, spiders, and even a snake once while hiking Rio Celeste. The free side even has some cool trail features like a balance testing river crossing. Don’t forget to give yourself some time to take some pictures too. Check out these HDR images and shots of the animals and trails that I took over a couple hikes:

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