On the northern coast of Babeldaob, bordered on the south by Ngaremlengui and on the east by Ngiwal and Ngaraard, Ngardmau is 30 square kilometer in size. The terrain includes: a thick fringe of mangroves along the coast; rolling hills in the interior rising to some of Palau's highest points; forests in the upper hillsides of the interior; and the Diongradid River Waterfall, Palau's tallest.

The village of Mgerdmau lies along the northern end of the state and consists of three traditional hamlets: Urdmang, Ngerutoi and Ngetbong. Traditional boat docks are found along the north coast, and a modern jetty extends west into the lagoon from the west end of Telong Hill. A road along the north side of the river connects the villages, while traditional paths extend outward to Ngaraard, Ngiwal, Melekeok and Ngaremlengui.

Bauxite mining operations took place in Ngardmau during the Japanese administration. Mining opertaion began in the mid 1930's and lasted until the early 1940's. The large tractsof land that were strip mined for bauxite ore, then transported by trucks and rail to the processing plant on the hill south of Ngardmau village can still be seen. At the processing plant, the ore was washed to remove soil, and then lifted to the loading tower on the jetty by gondola cars on an eleveted tram. A long jetty was constructed west of Telong Hill, extending out into the lagoon to load the ore for transshipment. The raw ore was then shipped to Japan's aluminium manufacturing centers.