Arenal Hanging Bridges is by far one of the greatest eco touristic projects of Costa Rica, where you can admire the exuberant primary tropical forest while treking on its 3.1 kilometers of trails and crossing 16 bridges (6 hanging bridges among them). There are over 200 species of birds, a vast diversity of reptiles like the famous Glass frog and mammals like monkeys, coatimundis, and sloths.