The Brussels Zoo was a short-lived establishment; according to a sign in the Zoology Museum in Brussels, the zoo opened in 1852 and closed in 1880. Nevertheless, 130 years after the zoo closed, the entrance gates still exist, complete with the inscription “Jardin Royal de Zoologie”.
Presumably it was founded by request of the King of Belgium so importance or status would have had nothing to do with it. It might even have been his menagerie before being a zoo but I am not sure about that. Anybody?
The site of the old Brussels Zoo was converted to a public park; Parc Leopold. I think that the park lake was a feature of the old zoo but none of the original zoo buildings remain. The excellent Brussels Natural History Museum is nearby.