Tsukuba (つくば市 Tsukuba-shi?) is a city located in Ibaraki Prefecture, Japan. It is known as the location of the Tsukuba Science City (筑波研究学園都市 Tsukuba Kenkyū Gakuen Toshi?), a planned city developed in the 1960s. As of October 1, 2012, the city has an estimated population of 217,315, with 90,151 households and a population density of 765 persons per km². The total area is 284.07 km². Mount Tsukuba, particularly well known for its toad-shaped Shinto shrine, is located near the city. Tsukuba is a twin city of Irvine, California, Milpitas, California, and Cambridge, Massachusetts in the United States of America.