What would be a likely natural feature in an extremely densely populated area of the world

Population density refers to the amount of population per unit area or unit volume. Most densely populated territories in the world are city-states and microstates. These territories usually have a small area, but with a high level of urbanization, and are economically stable. For these reasons, inhabitants draw nearer to them.

Compared to rural areas, urbanized cities provide ease of access to different basic resources needed by different households. The availability of good quality housing and infrastructure also attracts people to relocate and add up to the density population.

Relatively flat ground