Land reclamation from the sea in many riverine and coastal cities—Singapore, Hong Kong, Mumbai, and New York, among others—is one instance of the production, even fabrication, of space. The creation of space above or below the surface by tunneling or building is another. In New York City, for example, the Hudson Yards development west of Penn Station required the construction of a roof layer over the Long Island Rail Road yards as a crucial step in providing a foundation for future construction. The material elements of the urban environment play a crucial role in such projects.

Macau provides a different example of the creation of space, which is helpful for theorizing the concept of terrain. The region has nearly tripled in land size over the last century, with further land reclamation projects underway. The Cotai strip, where a number of casinos have been built, was entirely constructed through such infrastructure projects (Simpson 2014). Like Hong Kong, Macau has been a Special Administrative Region (SAR) since its incorporation into the People’s Republic of China. Yet Macau’s SAR status creates several interesting territorial anomalies. The University of Macau, for instance, was previously on Taipa Island, which is linked to the Macau peninsula by long bridges. In 2014, the university relocated to a new site that is twenty times larger than the old campus. Hengqin island, the site of the new campus, is a part of China—or, as it is confusingly described, the Chinese “mainland”—that is, not part of the old Portuguese colony of Macau. The site has been leased to Macau for the building of this new campus and is linked by a tunnel, even as further development projects unconnected to the university proceed. Hengqin itself is three times bigger than Macau, and is a special economic district within the Zhuhai special economic zone of Guangdong province. This means that the SAR of Macau, which is simultaneously part of China and not part of China (“two systems, one country”), leases part of a district of a zone of China which has become part of Macau for some purposes, but not for others. The island of Hengqin is a special economic district with tourism and other forms of development, but the campus has a different status from the rest of the island. This territorial configuration gives rise to all sorts of jurisdictional and geographical issues.

Macau’s development provides a key example of the complicated nature of political, economic, and cultural borders and the dynamic nature of territory, especially as the scales of the urban and the national collide. But the transformation of the landscape—tunnels, walls, roads, bridges, and land reclamation—equally shows the complicated interrelation of geophysical and built landscape elements. All of these issues need to be understood in a more three-dimensional way: the volume of these spaces is intimately related to the materiality of territory and the question of terrain.

Building on my previous books on territory (Elden 2009, 2013), I have begun to explore the question of terrain more systematically (Elden 2017). Terrain, I argue, is the best concept we currently have for understanding the complexity of territory in its material states. This materiality is in no sense a static outcome of previous processes—either geophysical or human transformations—but is dynamic and mutable. The complex interrelations of the geophysical environment and the built landscape can be understood as what Thomas Sigler (2014, 897), in his work on the Panama Canal, has called “the territorial palimpsest.” This is a term that wonderfully captures the overlapping, interactive nature of these transformed and transforming spaces.

Terrain is a crucial concept in physical and military geography. It is often understood as land form in contrast to land process, and it is used to describe the topography of dry land rather than the bathymetry of the sea bed. It is generally seen as a layer over deeper bedrock: simply the surface of the earth. This perspective is certainly three-dimensional, but its height and depth remain limited. Military geography, for instance, has examined how landscapes limit or enable military action, focusing broadly on the impact of the environment on the military. But to theorize terrain, we should reverse or challenge these limitations. Terrain is itself dynamic, a process. It includes both sea and land, and their complex interrelations in indeterminate, changing environments such as sea ice, glaciers, rivers, swamps, and marshes. It should also include airspace, for terrain is volumetric in nature; layering and the interrelation of layers are crucial to its determination. Following Rachel Woodward (2004), terrain can account for the impact of the military (among other state and nonstate actors) on the environment: how, in other words, human action transforms the terrain, without terrain’s physical materiality ever being entirely under control.

Territory, too, is a process rather than an outcome, a stake in political struggles rather than just their container. Terrain facilitates a grasp of the materiality of territory, integrating studies of built landscape with the geophysical: the continual making and remaking of territory. Often focused on state borders, territory more properly extends through the fabric of the state and can only be grasped as volume. Gastón Gordillo (forthcoming) has suggested that terrain is “the only spatial category that (in contrast to place, territory, or landscape) evokes material forms, volumes and textures that are not reducible to human control and appropriations.” Terrain is crucial to understanding the political practice of territory, and a useful way to comprehend the question of volume between geophysics and geopolitics.