Since it's a pretty average small zoo and the media largely speaks for itself, I've decided to simply give a brief statement rather than a full walk-through or comprehensive review.
The Pana'ewa Rainforest Zoo of Hilo, Hawaii, is aptly named; it is the only zoo in the United States located in a tropical rainforest climate. I was also pleasantly surprised by the admission price; it's free! Free zoos are rare, and Hawaii was one of the last places I would have expected to have a free zoo. I don't know if they receive municipal funding or if they are entirely dependent on donations and the like.
As I stated, the zoo is pretty unremarkable in terms of exhibits (mostly cages) and species (mostly small tropical animals that are commonplace in other American zoos). There are exceptions to both of these, however. The exhibit exception is a MASSIVE tiger enclosure for two tigers; I was stunned by its size, and I would be quick to argue that it rivals major zoos on the mainland for the title of best tiger exhibit in the country.
The species exception are the native Hawaiian birds. I'm pretty sure nene are held on the mainland, but two other species at Pana'ewa are not: the 'io, or Hawaiian hawk (Buteo solitarius) and Hawaiian short-eared owl (Asio flammeus sandwichensis). There also used to be Hawai'i 'amakihi (Chlorodrepanis virens) but when I visited the exhibit said "temporarily closed". Besides the 'io and pueo, there is also a *hybrid* lemur that, per studbook data, is over 90% a white-fronted lemur, an almost extinct species in North America.
The zoo certainly has potential, with both empty and underutilized space available for new exhibits and a climate that is conducive to keeping countless species. The question is whether that potential will ever be recognized, as small zoos usually lack funds for major renovation and often struggle just to keep their doors open. Whatever its future, Pana'ewa ekes out an existence as the only zoo on the Big Island and a final home for many confiscated pets and rescue animals.