The area on the Petersberg, where the Mainz-Kastel Zoo and the aquarium facilities are located today, is an abandoned quarry that was exploited in 1904 for the construction of the foundations of the Mainz Imperial Bridge. In 1924, a land mail carrier discovered it and founded the open-air facility together with friends.

The partly swampy, partly steeply sloping terrain became the site of the "Cyperus-Verein für Aquarien- und Terrarienkunde Mainz". The first aquarium house was inaugurated in 1933. Today, the open-air facility includes the aquarium and terrarium show house, ponds and a circular path. In the 1960s, the lower part was expanded into a zoo. In 1968, the "Association for the Preservation and Promotion of the Mainz-Kastel Zoo" was founded.

Today, the entire area is run jointly by both associations. The "Arbeitsgemeinschaft Biotop Petersberg" (Petersberg Biotope Working Group), founded in 1997, serves to preserve the site as a local recreation area for the AKK suburbs. The animals at the Mainz-Kastel zoo include goats, donkeys, sheep, ferrets, rabbits, domestic ducks, cats and water turtles.