Lake Coatepeque is one of the most beautiful natural features in El Salvador — a deep crater lake about 25 km south of Santa Ana that glows a vivid blue-green in good light. It fills a volcanic caldera formed by a series of eruptions between 57,000 and 72,000 years ago, a deep blue oval of water enclosed by steep forested walls, with the Santa Ana Volcano rising behind. The water is warm and good for swimming, and several lakeside restaurants offer access to the water along with fish and seafood.
The lake is privately ringed by the weekend homes of San Salvador's wealthy families, which limits public beach access somewhat, but the view from the rim road before you descend is extraordinary and worth the stop on its own. To reach the lake, take the road from the El Congo junction on the Panamericana; comedores along the water serve freshwater fish dishes.