Væksthusene, Aarhus Botanical Garden greenhouses (Tropical House)

Aarhus Botanical Garden was founded in 1873. Its present greenhouses grew out of the expansion of the university: the Botanical Institute, created in 1963 by Professor Kai Larsen, asked for land in the garden, which the city council granted on 8 October 1964. Under the agreement the land was provided free of charge for thirty years, in return for free public access. Built from 1968 to 1970 to designs by C.F. Møller and U. Bak, the greenhouses then comprised five linked houses of about 2,000 m², including an 18-metre-high palm house, and four climate zones.

In 2009 the C.F. Møller practice won the competition for their renovation and extension. The greenhouses closed in autumn 2010 and the foundation stone of the new building was laid on 26 May 2011. Funded by Aarhus Municipality, the Realdania foundation and the Nordea Foundation among others, at a cost given as 64 to 65 million kroner, the works ended with the official inauguration on 12 September 2014. The old palm house became a botanical information centre and a large tropical dome was added. Run by Aarhus University's Science Museums, the greenhouses thus shifted from research to public engagement; they passed two million visitors during their first ten years.

According to the architects, the complex covers about 3,586 m²: 1,586 m² for the new tropical house and 2,000 m² of renovated and remodelled original greenhouses. The 1970 building already followed a spiral plan inspired by the surrounding landscape.

The tropical dome, 18 or 19 metres high depending on the source and almost 20 metres across, was developed through computational optimisation to balance structure against energy use. Its shape and its orientation to the points of the compass give the smallest surface for the largest volume, admit as much sun as possible in winter and limit solar gain in summer. It is clad in air-filled ETFE cushions with built-in pneumatic shading. An observation tower and walkways let visitors look at the forest from the height of the treetops. Designed with C.F. Møller Landscape and the engineers Søren Jensen, the project received Aarhus Municipality's architecture prize in 2014.

The greenhouses offer a journey through four climate zones. In the tropical house, kept at around 80 per cent humidity, rainforests of America, Asia and Africa grow side by side; the cultivated plants include cacao, vanilla and sugar cane. A pool holds giant water lilies and water hyacinths, and butterflies fly freely, among them glasswing butterflies (Greta oto) from the rainforests of Central and South America.

The smaller houses present the vegetation of Mediterranean climates, deserts and tropical mountains. The old palm house, converted into a botanical information centre, contains a lecture hall, classrooms, exhibitions and a café, so that the greenhouses serve teaching as much as leisure.

The greenhouses stand in the Botanical Garden in the heart of Aarhus, and admission is free. Allow an hour to an hour and a half to walk through the four climate zones, climb the observation tower in the tropical house and stop at the café in the information centre. The Botanical Garden covers 21.5 hectares, including the 5 hectares of the Den Gamle By open-air museum, which is easy to combine with a visit. In winter the humid warmth of the tropical dome makes a sharp contrast with the Danish climate.