Frederick Law Olmsted's Map of Central Park

Origin
Frederick Law Olmsted (April 26, 1822 – August 28, 1903) was an American landscape architect, journalist, social critic, and public administrator. He is popularly considered to be the father of American landscape architecture, although many scholars have bestowed that title upon Andrew Jackson Downing. Olmsted was famous for co-designing many well-known urban parks with his senior partner Calvert Vaux, including Prospect Park and Central Park in New York City, as well as Elm Park (Worcester, Massachusetts), considered by many to be the first municipal park in America.

Effect
When the map is placed on a patch of dirt, plants will begin to sprout from the ground. The longer it is on dirt, the quicker they grow and the more they spread. The plants are completely normal.