If you happen to be traveling between Cienfuegos and Trinidad and don't mind a slow/bumpy 1-2 hour drive into the Escambray Mountains, consider a trek in the small but scenic Parque El Nicho. Its series of freshwater cascades has become a highlight for locals and visitors to the region, offering a brief 25 minute hiking trail, beautiful views of Central Cuba and the valley below, and access to clear, refreshing natural pools that are an excellent escape from the country's sometimes-oppressive heat.
It's true that the falls themselves are not particularly extraordinary (at their highest they drop from about 15 m), and that the park can get crowded quickly during the hottest months. That said, there are a few ways to get the most out of the experience. First, come early, which will allow you time to appreciate the uppermost pool in relative tranquility. Second, look for the unmarked but well-trodden path that leads to the lower pools, which tend to stay less-crowded throughout the day. If you don't have access to your own vehicle (or don't want to navigate the roads by yourself), you can catch a bus or a personal taxi (40-60 CUC round-trip) from Cienfuegos to El Nicho, and the cost to enter the park is nominal. Then just make sure you've brought your swimming gear and enjoy a refreshing day exploring the wilderness of Central Cuba.