Burgers' Bush

The idea of a covered tropical rainforest took shape as early as the late 1960s in the mind of Antoon van Hooff, director of Arnhem's Burgers' Zoo, who wanted a convincing environment free of interior pillars that might break the visitor's sense of immersion. The project only became technically achievable in the early 1980s, once plastic materials suited to air-cushion roof construction became available.

Burgers' Bush opened on 1 June 1988, inaugurated to an African drum roll by Pieter van Vollenhoven, a member of the Dutch royal family. The concept marked a break with convention in the zoo world: instead of viewing animals in enclosures, visitors sought them out, with relative freedom, within dense tropical vegetation that already numbered several hundred species. The response was immediate — the zoo's visitor numbers doubled within a year — and the idea spread to zoos worldwide.

The building's engineering earned it the Dutch Steel Prize in 1988 and the European Steel Prize in 1989. Thirty years after opening, in 2018, Burgers' Bush was still being presented by the zoo as a founding project of its identity.

The challenge was to roof nearly a hectare and a half without a single interior column, a condition considered essential to preserving the illusion of a real forest. The solution relied on hundreds of air-cushion roof elements, a then-recent technique that allowed wide spans to be covered with a lightweight structure — novel enough to be recognised with two consecutive steel-industry prizes.

Inside, a tropical climate is maintained continuously between 20 and 24°C, with humidity of 70 to 100%; every night, roughly 80,000 litres of water are sprayed into the air — three to four times the Netherlands' average annual rainfall — and a waterfall helps regulate temperature and humidity throughout the hall.

Planted young in 1988, the tropical trees have since grown as tall as twenty metres, reproducing at building scale the successional stages of a real rainforest, from pioneer vegetation to primary canopy. The greenhouse today holds around 1,500 plant species, including bromeliads and figs; upkeep requires pruning about 25,000 kilograms of plant matter a year, which is redistributed as food for the site's herbivores.

The animal population is just as varied: freshwater rays and catfish, tilapia, anoles, basilisks, iguanas, turtles and caimans, nocturnal whistling frogs, fruit bats and Seba's short-tailed bats, small-clawed otters, aardvarks, and more than thirty bird species living free. Several endangered species breed successfully here, contributing to European zoo-coordinated conservation breeding programmes.

Two kinds of route coexist: a wide, paved main path, accessible to wheelchairs and strollers, running past the larger animals' habitats, and narrower, winding adventure trails where visitors cross streams on stepping stones in search of more elusive species.

The humid heat, dense foliage, sounds and smells add up to a full sensory immersion that sets Burgers' Bush apart from a conventional botanical glasshouse — visitors come here as much for the wildlife as for the plants.