美济礁
Located south-east of Mischief Reef (), Second Thomas Shoal is near the centre of Dangerous Ground in the north-eastern part of the Spratly Islands; there are no settlements north or east of it. It is a tear-drop shaped atoll, long north–south and fringed with coral reefs. The coral rim surrounds a lagoon which has depths of up to and is accessible to small boats from the East. Drying patches are found east and west of the reef rim.