 The Arakawa River runs across the border with Kita-ku to the south.As of May 1, 2010, registered population was 516,409, including 20,808 alien residents, continuing a trend of population growth in the city since 1933 when the city was founded.There has been a gradual increase in the number of non-Japanese residents living in the city because of the convenient location to Tokyo and relatively low rent.