Mainau, Flower garden island in Constance, Germany

Mainau is a drop-shaped island of about 45 hectares in Lake Überlingen, the northwestern part of Lake Constance, in the Konstanz ward of Litzelstetten. It measures roughly 610 metres north to south and 1,050 metres west to east, with a shoreline of about three kilometres. Its highest point, at 425 metres, is the Großherzog-Friedrich-Terrasse, a former water reservoir on the Vogelherd. The gardens hold an arboretum of 500 tree species, a rose garden, Mediterranean terraces and dahlia fields.

Mainau was long held by the Teutonic Order before passing to the Grand Duchy of Baden; Frederick I laid out the arboretum from 1856, and seeds of the giant sequoia arrived from California in 1853, planted in 1864. The municipality of Litzelstetten, including the island, was incorporated into Konstanz on 1 December 1971. Since 1974 the island has belonged to the Lennart Bernadotte Foundation, set up by Count Lennart Bernadotte, who died in 2004.

Lennart Bernadotte, a Swedish prince who lost his royal title after marrying a commoner, took over the island in 1932 and turned it into a public garden. His family still lives in the palace, and the Bernadotte name remains part of the island's identity. Visitors can see the family's residence and the gardens they maintain.

Mainau is reached on foot by a bridge from the western mainland shore; a car park sits on the mainland at that western entrance, and ferries from Konstanz, Meersburg, Unteruhldingen and Kreuzlingen dock at two landing stages on the east side. One lane of the bridge is reserved for residents, restaurant guests and staff. The island lies about four kilometres north of Konstanz's old town.

The island's highest point, at 425 metres, is by the Großherzog-Friedrich-Terrasse, a historic water reservoir on the Vogelherd. The garden's arboretum holds one of Germany's oldest dawn redwoods, a Chinese species planted in 1952 as a 70-centimetre sapling in the shore garden.