Underground Built Heritage

Defining Underground Built Heritage (UBH)

Within the multidisciplinary framework of Underground4Value, participants shared concepts and perspectives from diverse disciplines to build a cross-fertilised and coherent definition of Underground Built Heritage (UBH). The ambition was to develop a taxonomy aligned with the terminology used by the UNESCO global community, which could also serve as a foundation for potential international recognition of UBH as a distinct heritage category. The first step in this process was to define, clearly and comprehensively, the object of valorisation and the reasons for its significance.

A central issue was clarifying the meaning of the term underground. The word itself, as defined in the Cambridge Dictionary, refers simply to what lies “below the surface of the earth, below ground.” Yet this spatial description alone is insufficient for heritage purposes. The underground is not necessarily composed of voids or cavities; rather, it is part of a dynamic system shaped by continuous interactions between endogenous (internal) and exogenous (external) processes of the Earth. These processes constantly remodel both surface and subsurface landscapes, such that today’s built environment may one day become tomorrow’s underground, rediscovered and reinterpreted as heritage. 

When considering heritage, attention is directed specifically to those parts of the underground that embody cultural value. To capture this meaning, heritage must be understood in an expanded sense: one that integrates historical, cultural, and ecological dimensions across long temporal scales. While historical and cultural values are often readily recognised, the ecological perspective is equally crucial, especially in anthropised spaces where human presence and activity have transformed environments into meaningful cultural landscapes.

The concept of built heritage is particularly relevant here. It encompasses not only architectural monuments but also landscapes, sites, and material references that embody local history, practices, traditions, and collective identity. According to ICOMOS, built cultural heritage includes “cultural buildings, historic landscapes, and archaeological sites: a quantitatively minor part of the built environment which the contemporary generation recognises as having ‘cultural values’ and therefore merits special protection so that it may be enjoyed today and transmitted to future generations.”

This definition should not be reduced to a simple combination of “built” and “heritage,” nor equated solely with architectural remains. Rather, it refers to historical heritage in its broadest territorial and ecological sense. Its value lies not only in providing a synchronic reading of a community’s past but also in offering a diachronic perspective, revealing what has endured, what has changed, and what may continue to evolve in the future.

Seen from this perspective, underground heritage emerges as a diachronic narrative of continuous physical, functional, and cultural transformations. It is therefore an integral part of the wider category of built heritage and can be conceptualised as a specific subcategory: Underground Built Heritage (UBH).

Accordingly, UBH may be defined as:

Three types of building activities, namely architectural, urban and landscape heritage below the surface of the earth, which the contemporary generation resolves have “cultural values”.

A Glossary – Relevant Terms for Understanding Underground Built Heritage (UBH)

To situate Underground Built Heritage (UBH) within a wider conceptual framework, it is important to revisit some key definitions of heritage and built heritage.

The notion of Built Heritage stems from the broader category of Cultural Heritage, as first codified by UNESCO in the 1972 Convention Concerning the Protection of the World Cultural and Natural Heritage [UNESCO, 1972]. Cultural heritage, in this foundational text, is classified into three main categories:

  • Monuments: architectural works, monumental sculptures and paintings, archaeological structures, inscriptions, cave dwellings, and combinations of such features recognised for their outstanding universal value in history, art, or science.
  • Groups of buildings: ensembles of buildings, either connected or separate, that hold outstanding universal value due to their architecture, homogeneity, or integration into the landscape.
  • Sites: works created by humans, or jointly by humans and nature, including archaeological areas, which have outstanding universal value from historical, aesthetic, ethnological, or anthropological perspectives.

Since 1972, the concept of cultural heritage has significantly evolved. The European Parliament (2018) framed it as “the legacy of physical artefacts and intangible attributes of a group or society inherited from past generations, maintained in the present, and bestowed for the benefit of future generations.”[EP, 2018]

A particularly influential contribution came from the Council of Europe’s Faro Convention (2005), which broadened the definition of cultural heritage to include “a group of resources inherited from the past, which people identify, independently of ownership, as a reflection and expression of their constantly evolving values, beliefs, knowledge, and traditions. It includes all aspects of the environment resulting from the interaction between people and places through time.” [Council of Europe, 2005]

From this perspective, cultural heritage is a subcategory of heritage, which itself can be defined more broadly as:
“any asset or group of assets—natural or cultural, tangible or intangible—that a community recognises for its value as a witness to history and memory, and which requires safeguarding, protection, promotion, and dissemination.”

This distinction highlights two complementary dimensions [UNESCO 2003]:

  • Tangible Cultural Heritage: physical artefacts produced, maintained, and transmitted inter-generationally in a society. It includes artistic creations, built heritage such as buildings and monuments, and other physical or tangible products of human creativity that are invested with cultural significance in a society.
  • Intangible Cultural Heritage: oral traditions and expressions, including language as a vehicle of the heritage; performing arts; social practices, rituals, and festive events; knowledge and practices concerning nature and the universe; traditional craftsmanship. 

UNESCO further elaborates that intangible heritage is:

  • Traditional, contemporary, and living at the same time 
  • Inclusive: we may share expressions like those practised by others 
  • Representative: it thrives on its basis in communities and depends on those whose knowledge of traditions, skills and customs are passed on to the rest of the community, from generation to generation, or to other communities
  • Community-based: heritage when it is recognised as such by the communities.

Together, these definitions reveal that heritage, whether tangible or intangible, is not static. It evolves through continuous interaction between people, places, and practices, shaping both identity and memory. Within this evolving framework, Underground Built Heritage can be positioned as a specific and meaningful subcategory of cultural heritage, emphasising its tangible and diachronic character while also acknowledging its ties to intangible values and community significance.

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