Whatever time of year you visit Mainau Island in Lake Constance, the sheer botanical diversity and abundance of brightly coloured flowers across 45 hectares are sure to make a big impression. The park, populated with trees over 150 years old, is just as striking as the tropical palm and citrus plant collections. And no visit to the island is complete without a tour around the baroque palace grounds and church, and a trip to the butterfly house with its 40 exotic species.