A kilometer beyond the turnoff to Dos Hermanas and the Mural de la Prehistoria, a dirt road twists up to the mountain community of Los Aquáticos, founded in 1943 by followers of visionary Antoñica Izquierdo, who discovered the healing power of water when the campesinos (farmers) of this area had no access to conventional medicine. They colonized the mountain slopes and two families still live there. It's accessible only by horse or on foot. Most of Viñales' casas particulares (private homestays) can organize tours.
You can also go it alone. Although no signs mark the path, there are plenty of homesteads en route where you can ask the way. From the main road follow a dirt road for approximately 400m before branching left and heading cross-country. You should be able to pick out a blue house halfway up the mountain ahead of you. This is your goal. Once there, you can admire the view, procure grown-on-site coffee and chat to the amiable owners about the water cure. After your visit, you can make a loop by returning via Campismo Dos Hermanas and the Mural de la Prehistoria cliff paintings; it's a wonderfully scenic route (the complete Los Aquáticos–Dos Hermanas circuit totals 6km from the main highway).