The northern coast of the island is home to most of Aruba's natural attractions. The largest of these is the Arikok National Park, which covers 18% of the island and contains several noteworthy sites accessible by a network of hiking trails. Here, visitors will find the bat-filled Quadirikiri, Fontein, and Huliba Caves. The Quadirikiri Cave is known for the holes in its roof that allow natural light to stream into its two chambers. The Fontein Cave is marked by stalagmites and stalactites and Arawak Indian wall drawings; and the dark, 300-foot-long Huliba Cave is also known as the Tunnel of Love cave because of its heart-shaped entrance.
To the north of the Park are the Ayo and Casabiri Rock Formations, each of which is a dramatic, almost eerie cluster of boulders that seems to spring out of nowhere. Both areas are accessible by safe hiking trails that wind among the boulders. Also in this area is the Rock Wish Garden, where tourists come to build their own devotional towers of stones in the hopes of having wishes granted. Near here, on the coast, is the site of the Natural Bridge, the 25-foot-high, 100-foot-long span of coral limestone that once stretched over a cove was long one of Aruba's most photographed sites until its collapse in 2005. A similar, though smaller, bridge remains nearby.
Birders will want to visit the nesting sites on the San Nicolas Bay Keys, off the southeastern shore of the island, where they can spot the Aruban Cayenne tern along with egrets, herons, stilts, yellowlegs, and many other birds. The Bubali Bird Sanctuary, located near Eagle Beach across the street from the Old Dutch Windmill, is home to 80 species. Also near here is the Butterfly Farm, where thousands of butterflies, from 40 different species, are bred.