At more than 140 years old, Hong Kong zoo is home to almost 400 animals, including three-year-old twin orang-utans and one very bored-looking sloth.
Little seems to have changed since the Hong Kong Zoological and Botanical Gardens' inception in 1871, according to the Society for the Prevention of Cruelty to Animals. But the city is studying how to modernise it.
"It's like a menagerie from the turn of the last century," said Dr Jane Grey, the deputy director of the SPCA. "The facilities are very outdated, inadequate and overcrowded."
Watch: Hong Kong zoo under fire for "outdated" facilities
Flamingos are packed into their enclosure tighter than rush-hour commuters on the MTR and their water bowls are made of plastic, which can spread disease.
Sloths are given rocks to climb that they can't grab on to.
And the zoo's pride and joy, a family of orang-utans - with mother and twins Wan Wan and Wah Wah all born in Hong Kong - are in separate enclosures with little more than a few palm trees and a rope to engage with.
The government-run zoo, which is free to enter, is tucked behind Central on the slopes of Victoria Peak. It is subject to a detailed study of its long-term development plan, which the Leisure and Cultural Services Department commissioned in January.
Stakeholders consulted by the Kadoorie Institute of the University of Hong Kong, which will produce a report in December, include the SPCA, Animals Asia and Orangutanaid - all of whom have expressed sincere doubts over the welfare of its animals and recommended that the park be returned to its original status as a botanical garden. "Hong Kong is not the right place to keep animals," said Karina O'Carroll, the animal welfare education manager of Animals Asia, who questioned whether it was appropriate to breed animals at such a small zoo. "Conditions have to be vastly improved," she added.
The zoo, which first began keeping animals in 1975, boasts a strong conservation ethos and currently hosts 10 endangered species. This year, two red-handed tamarins were introduced to the zoo. The monkeys come from the Amazon and are on the International Union for Conservation of Nature's red list of threatened species, meaning they are critically endangered.
In 2010, a male orang-utan named Vandu arrived from Hungary to mate with the zoo's female Raba, who had twins. She was unable to feed them, and the twins were "rejected".
They now sit in a separate enclosure facing their estranged mother.
"Sadly, the captive orang-utans at the zoo here bear little resemblance to their wild cousins," said Mara McCaffery, founder of Orangutanaid.
"So for me this has nothing to do with 'conservation' of the species for future generations, which is what many zoos purport to be doing."
She said the zoo's orang-utans were "overweight, mentally unstimulated and bored".
A leisure department spokesman said the zoo "attaches great importance to the well-being of the animals under its care as members of the World Association of Zoos and Aquariums".
Zoo manager Susan Tam On-kei explained: "As members, we have to adhere to a code of ethics. But the organisation recognises diversity across the world - there are no universal standards."
Grey claimed that these guidelines were not very strong. "It really depends on what level of welfare you want," she said.
"If Hong Kong wants to consider itself a world-class city then it has to have world-class animal welfare."