Internationale Gartenbauausstellung 1973 Hamburg, known as IGA 1973, was the second BIE-recognised Horticultural Expo to take place in Hamburg, a decade after the first. The Expo received recognition from the General Assembly on 17 November 1970, and was open to the public between 27 April and 7 October 1973, during which time it received 5.8 million visitors. As with the previous edition, IGA 1973 took place in Hamburg’s “Planten un Blomen” park.

The Expo’s organisers drew on Hamburg’s ecological planning strategy, which was supported by the President of the Federal Republic Gustav Heinemann, who opened the event. In his inaugural speech, President Heinemann emphasised the importance of green spaces in city centres and described IGA 1973 as the “window to the city”.

Since IGA 1963, the site had undergone several upgrades and modifications, with a redefinition of the Expo site concept, a focus on visitor experience and the insistence on “not getting feet wet.” A single Expo site was created by joining Planten un Blomen with the Old Botanical Garden and the Wallanlagen (fortifications). This was achieved by tunnelling part of Marseiller Strasse and creating a garden crossover between the two sides, in what was an early model of a green bridge. The connection permitted the site’s miniature railway to be extended, taking visitors across the whole site.

Additionally, two major new buildings – the Congress Center of Hamburg (CCH) and a 108-metre hotel, were built on the edge of the site, transforming its panorama.

In the site itself, the exhibitions had evolved compared to IGA 1963, with a focus on new forms and colours to reflect a more industrialised world. Art played a significant role in IGA 1973, with visitors enjoying a vast programme of culture and entertainment throughout the 164 days of the Expo. As part of this programme, young artists from Hamburg were asked to contribute to the Expo by meeting with the public and presenting their own visions.

With 50 international participants, visitors were able to discover plants and gardens from across the world, with notable examples being Sweden’s wooden playground, Italy’s Tuscan landscape and a perennial British garden.

Following the Expo, many key features remained in the park, including the “Bullerberge” landscaped play area designed by Wido Buller, as well as the Water Organ, an impressive array of brightly lit, angled fountains. The Japanese Garden, designed by Joshikuni Araki, and Karl Plomin’s Spring and Tropical Gardens are also highlights of Expo 1973 that continue to feature in the modern-day park.