Sphinx Head is a site of conspicuous cliffs up to 67 metres (220 ft) high, about 16 kilometres (9.9 mi) SSW of Low Point.

Two flat-topped hills south of Sphinx Head rise to a maximum height of 79 metres (259 ft).

[2] Administratively, Marchinbar Island is part of Gumurr Marthakal Ward of East Arnhem Region.

The only settlement is Martjanba, a small family outstation on Jensen Bay in the northern part of the island.

This discovery has been of interest to those historians who believe it likely that seafaring people made landfall in Australia or its offshore islands after Aboriginal settlement and before the first generally accepted such sighting, by the Dutch sailor Willem Janszoon in 1606.