The Morton Arboretum is Lisle's main reason to visit. Founded in 1922 by Joy Morton of Morton Salt, it covers about 1,700 acres of trees, gardens, prairie, and woodland trails, with a research library and herbarium behind the public walks.
It is good in every season: spring blooms, summer shade, autumn colour, and winter walks through bare oak and conifer collections. Give it more time than you think; it is much larger than a suburban garden.