Nature has blessed Costa Rica in its gorgeous landscapes, fertile fields, and a thousand other bucolic miracles. Río Celeste, for example, is like no other river in the world. This stream gets its sky-blue color from rocks along its bottom that are rich in silicon, oxygen, and aluminum, and when the sun strikes the murmuring waters, the color is sublime. Be sure to visit El Teñidero, the spot where two tributaries merge. Upstream from the nexus, the waters of both are clear, but when they meet at El Teñidero, their chemistry combines to make a very unusual hue. A one-mile hike leads to a pristine lagoon in similar shades and an overlook above the bluest waterfall you ever saw.