Marontik was the largest human community on Earth in approximately 100,000 BCE, having grown significantly within the preceding two centuries. It was located at the confluence of two great rivers, and mostly consisted of wooden shacks and mud huts, some three or four stories tall. They were arranged on either side of alleys branching into other alleys, winding in no particular direction. The city spread over dozens of square kilometers, and had an extensive network of underground catacombs. Local guides offered tours of these catacombs for visitors. The humans used various types of balloons and airships for transport across the city. It was also home to a collective of guides led by a matriarch. Chakas and Riser were part of this group.
The Forerunner Saga gives several vague suggestions as to Marontik's location on Earth. In Halo: Primordium, the city is stated to be located deep inland and surrounded by grasslands. Mara's species are stated to have lived in highlands some distance north of the city. Fossils of Gigantopithecus have been found across South and Southeast Asia, suggesting that Marontik may have been located somewhere in or near this region. The "two great rivers" between which Marontik lay may have been the Tigris and the Euphrates, which would place the city in prehistoric Mesopotamia. Though humanity is theorized to have originated in ancient Kenya, Mesopotamia is considered to be a cradle of civilization. The biblical Garden of Eden, where God created mankind, is often suspected to have been situated at the headwaters of these rivers. However, in Halo: Rebirth it is stated that the Portal at Voi, located in modern-day Kenya, was "not far" from Marontik's location; however, the ambiguity of the wording would this allow the city to be reasonably placed in Mesopotamia.