Designed in a way that makes cages (almost) obsolete, the BioParc in Valencia, Spain allows an unobstructed view of the animals, and lets you get close to them... uncomfortably close, sometimes. It feels like there are no fences and the animals roam free.
Except for the areas where the Gorillas, Leopards and lions are. There a glass separates you from the animals. The BioParc opened its doors in 2008 and currently, it's home to 4000 animals of 250 species, with a special focus on the fauna of Africa.