Located in Incheon City, tidal-flats in Song Do were formerly very extensive (>5000 ha), and part of the massive Gyeonggi Bay tidal-flat system. The Gyeonggi Bay system has a tidal range during spring tides of >9m, and broad tidal-flats that until the 1980s were continuous at low tide along very approximately 100 km of coast north-south and around large near-shore islands, north to include Yeongjong and Ganghwa Islands, and south to Namyang and Asan Bays.
There is now only one large and complex area of tidal-flat remaining at Song Do and lies between Song Do to the north, and Sorae and Oido towns to the south, and is comprised of approximately 800 ha of tidal-flats and 400 ha of sea-shallows at low tide, fed by the Sorae creek.