Get down and dirty on an unforgettable spelunking experience at the Venado Caves, 45 minutes from La Fortuna. The caves were formed some 15 to 20 million years ago by tectonic shifting and erosion from underground streams. In them, you’ll see stalagmites and stalactites galore, and get the chance to check out colorful frogs and fascinating marine fossils and learn about the bat communities hanging right over your head. The experience is real (and really humid)—so wise adventurers bring insect repellent, knee pads, and an extra change of clothes. Waterproof your camera, too.