According to 'The Guinness Book of World Records' where is the world's smallest park located?

Mill Ends Park is a tiny urban park located in the median strip of SW Naito Parkway, approaching esplanade along the Willamette River near SW Taylor Street in downtown Portland, Oregon, United States.

The park is a small circle 2 ft (0.61 m), with a total area of 452 sq in (0.292 m2). It is the smallest park in the world, according to the 'Guinness Book of Records', which first granted it this recognition in 1971.

In 1948 the site was intended for a light pole. When the pole failed to appear and weeds sprouted in the opening, Dick Fagan, a columnist for the 'Oregon Journal', planted flowers in the hole and named it after his column in the paper, "Mill Ends".

Fagan's office in the Journal building overlooked the median in the middle of the busy thoroughfare that ran in front of the building. The park was dedicated on St. Patrick's Day, 1976, as "the only leprechaun colony west of Ireland," according to Fagan.

Fagan told this story of the park's origin: He looked out the window and spotted a leprechaun digging in the hole. Fagan wished for a park of his own, but since he had not specified the size, thus the leprechaun gave him the hole.

The small circle has featured many unusual items through the decades, including a swimming pool for butterflies, complete with diving board, a horseshoe, a fragment of the Journal building, and a miniature Ferris wheel, which was delivered by a full-size crane. The park continues to be the site of St. Patrick's Day festivities.