Rio Celeste y Los Teñideros, located within Tenorio Volcano National Park, offers a stunning natural spectacle of a vibrant blue river, but requires a moderate level of fitness for its 3-4 hour hike on often muddy and uneven trails to the waterfall and the color-changing 'Teñideros,' making it generally inaccessible for wheelchairs or strollers. While possible to visit solo, a local guide can significantly enhance the experience by explaining the unique geological phenomena and spotting wildlife; no guide is mandatory. The ideal time to visit is during the dry season (December-April) for clearer water and less challenging trails, as heavy rains can diminish the iconic blue hue and make paths very slippery. Expect an approximate cost of $12-15 USD for park entrance for foreigners, plus optional guide fees and transportation. Visitors should bring sturdy hiking shoes, water, insect repellent, and rain gear, as facilities within the park are basic and swimming is prohibited.