Hike the Rio Celeste in Costa Rica

A long drive and a muddy trail may not sound appealing at first, but the first glimpse of this brilliant turquoise river makes it all worth it. From the town of Bijagua, take the unpaved road with signs towards Tenorio Volcano National Park and Rio Celeste. Eventually you'll come to a parking lot on the right where the entrance is, marked "El Pilon" station. Here you'll buy your ticket ($10) and can rent rain boots for the muddy trail if desired. Trail runners or hiking boots will do just fine though, and there is a spigot to wash them off at the end. 

The walk begins on a paved path through sparse brush, eventually becoming dirt, gravel, and mud through dense jungle. First you'll come to a turn-off for the waterfall, or catarata, but many recommend you follow the main trail all the way to the end and work your way back, stopping at the viewpoints. 

The end of the main trail is where you can witness the two colorless rivers, Buenavista River and Sour Creek, joining together and forming the Rio Celeste. This point is called "teñideros" or dyers. The bright blue color is a result of Mie scattering, a physical phenomenon in this case when a drop in Ph levels causes aluminosilicate particles to enlarge and absorb all light except blue light, which is reflected. Therefore, the river is brightest in sunlight, so check the weather when you go. In the rainy season, the river may actually be a muddy brown.

Working back from the farthest point, you'll cross a small wooden bridge that takes you over the water, where you can get an up-close look. From there, the "borbollones" or hot springs are where you can see volcanic activity bubbling to the surface (accompanied by that sulfur smell). A blue lagoon and a "mirador" or viewpoint over the river valley are next, then finish by turning down the steep stairs towards the waterfall. 

On the way back, vendors selling fresh coconut water are a welcome sight, or you can eat lunch at the nearby cafe. 

The trail opens from 8 am to 4 pm with the last entry at 2 pm. 

You can't swim in the water in the park, but down the road from the parking lot is a section where you may swim if you wish.