File this one under "things to see next time I am in El Salvador." The CNN website provides this video of the Los Tercios waterfall in Suchitoto. From the Suchitoto Municipal Tourism Office website:
The Los Tercios Waterfall is just a 1.5 km walk from the city center. Its uniqueness and beauty lies in the vertical wall behind the water that is composed of large hexagonal columns of rock. This very rare rock formation is the result of nearby volcanic activity, although numerous folkloric legends also claim to explain the origins of the shape of the rocks.
Los Tercios has water between May and November, although it is worth a visit between December and April too in order to see the stones most clearly.
For more about what to see and do in Suchitoto, visit the very helpful website of the Municpal Tourism office.