The botanical gardens, frequented by leading experts like Linné, were founded in 1673 by the Honourable Society of Apothecaries of London. The land was leased to Hans Sloane and used for students' experiments. The gardens still have an educational role and continue an important research programme into more than 5 000 medicinal plants. If you're in London in May, don't miss the Chelsea Flower Show Week held in the gardens.