A second characteristic of a heterotopia is something that serves a specific unchanging function within society but which spatial location and rituals change most radically in relation to the ideologies or dominant values of each age. Examples of such spaces of heterotopia are cemeteries, brothels, or prisons. These institutions function in all societies in diverse forms, however, their design, location and practice depend on its relation to the moral and social order of the disciplining power in each era. It is through the changing locations and habits of use of these places of anomaly or “periphery” that gives shape to the center, the legal and "normal".
This characteristic of heterotopia, as both a constant and variable allows us to trace and compare the epistemic breaks between different social regimes.
An ancient city like Hanoi with its intermittent wars of territory and rebellion, its agrarian economy and values and oral traditions, and the abrupt change of written language from Han Nom to Quốc Ngữ, has left many voids in recorded history. The social uses of space throughout the city have changed through the ages leaving ambiguous traces for historiography other than as archeological sites. Hanoi and its streets is a substrate of homes as commerces built upon foundations of other homes upon commerce and family altars, all the way through time. In a millennial city like Hanoi, except for the few clearly marked spaces clearly dedicated to the operation of the state, what space is not a Heterotopia? In other words, in a place where every space is saturated with memory without a continuous record, what can be used as a constant in order to reference and compare cultural and ideological changes? Belonging to its territory, Son ta has been used throughout ancient history in a multiplicity of forms up to the present, and has marked on its body in each form of every major dialectical change in this society.
During the feudal period lacquer was used as a protective and decorative skin for wooden objects in temples or for everyday use. During the colonial period, son ta was introduced as a image making medium as the concept of beaux arts and artistic authorship was introduced to Vietnam. During the revolutionary period as painting, this medium was charged with nationalism and propaganda. In the present day, after Doi Moi coinciding with international postmodernism, is a liminal period of changes in form and reflections on its own history.
With its qualities related to time, its many layers of building up (or construction) to the sanding away (or erosion), I liken Vietnamese son ta to a type of palimpsest, an ancient tablet or manuscript which preserves traces of writing that has been erased or written upon-- both being relevant vestiges and testimonies of another time that is barely discernable and entirely open to interpretation.