Hard to reach, but incredibly rewarding when you get there, Semuc Champey is a magical place. It is a 300 meter stretch of a river where a natural limestone bridge consisting of numerous pools has been formed. Most of the water flows below this bridge, but a decent bit of it fills the pools and offers an amazing place for swimming and chilling. It was very reminiscent of Plitvice Lake National Park in Croatia, just on a smaller scale and more enjoyable since you could take a dunk in these fantastic pools.
