The amphitheatre in Arles, Provence, is an intriguing example of how town spaces change over the years. This Roman structure was transformed into a mini-city following the fall of the empire in the 5th Century. As the Gauls plundered various treasures from the city’s institutions, the inhabitants retreated back into the defensible oval shape of the amphitheatre. In time this fortress morphed into a highly compact settlement, with over 200 individual houses and twelve churches.

Such a dramatic re-appropriation owes its story partly to the construction methods its craftsmen employed. Roman culture depended on the idea of civic architecture to institutionalise the power it held over its inhabitants. Each Roman city was essentially the same. All had two main streets – always called the Cardo and Decumanus – and similar types of buildings within the city: forum, amphitheatre, temples, you get the idea. The notion (the idea of the Ecumene, or inhabited world) was that this empire of similar cities upheld the Roman way of life.

To be Roman required a Roman city. As such, the builders of amphitheatres such as the one in Arles took care to create durable, elegant and civic buildings. The builders brought stones from beyond the local area – such that the building became more durable than the local vernacular buildings, and used clever technologies to ensure their longevity.

To me, the use of the amphitheatre in Arles as a mini-city is interesting principally for the cultural attitudes that its re-appropriation entails. The soil of the amphitheatre was, after all, a place in which a society watched its slaves fight to the death in a ritual of screaming, testosterone and violence.

Yet, the need for survival caused the individuals of that culture to overcome an institutionalised understanding of the amphitheatre, and make it a place in which all the difficulties, dramas and activity of a city life could be lived out. Instead of deserting Arles for the wilderness, these citizens wanted to maintain the idea of their city life, and achieved it through the conversion of this building.

Further, the amphitheatre offered the successful template for a mini-city, not only because of its size, but also because the people already understood it as a place of gathering. It formed an enclosure for them against the outside world, and maintained a life for its inhabitants until the nineteenth-century.

Hopefully this example begins to show the complexities in the re-appropriation of spaces. At the other end of the scale, one can pick out the developer-led culture of building offices in London during the 1980s, many of which are being torn down now with the intention of making spaces even more profitable.

Take City Road Basin in Islington. This three-storey 1980s campus of blue steel and brick, air-conditioned and artificially-lit offices is being replaced after just 25 years, for a new eight-storey complex.

Had these '80s offices been constructed as compact structures, letting natural daylight into all parts of the building, with natural ventilation, and an easy-to-edit system of walls inside, they could have remained useful. Architecture that is re-appropriable grants sustainability; you don’t have to waste huge resources every thirty years on re-building the city.

The idea of re-appropriation leads one to question whether architecture really should stand for such efficient and specific functions, particularly in modern times. The amphitheatre in Arles was successful because it had a set of simple abstract conditions: boundary, entrance, exit, inside and outside. These abstract qualities had an original character for its users, but also provided scope for re-interpretation. A simple oval enclosure allowed for those inside to feel united under a common cause.

This week's Love Art After Dark event at the Fitzwilliam saw the space of the gallery taken over. But what would be a proper re-appropriation of the Fitzwilliam? Obviously, one could go in there and do what one wanted in the space, but what might mass culture, an ethos, turn a museum into in the future?

To begin to see this, I think you need to understand what the Fitzwilliam Museum was built for. To me, the building acts as a vestibule between people passing though the city, and the permanent university.

It was built as a place for the University to exhibit its artefacts to people, and as a splendid area to enjoy the pleasures of life. The museum is not about learning, per se, but instead about constructing a narrative for visitors. This narrative starts with the steps outside, then the beautiful portico, then with the organisation of galleries, and smaller narratives in the positioning of pictures.

The greatest re-appropriation that we have been able to give to the Museum in modern times is the use of audio-guides, which give a more detailed narrative through the exhibition.

With sensitivity to these abstract ideas of what this building is, and means, to us, the best re-appropriation that I can conjure for a Fitzwilliam in the distant future is that of the tomb or cemetery.

Normally we bury our dead in the ground, but perhaps something could change that culture towards some kind of Anglo-Saxon burial with one’s splendid possessions.

When we’ve filled up all the graveyards in our city, perhaps we’ll look to our aged museums as immortal boxes in which we could install multilevel caskets dedicated to the eternal rest of others' memories and the narratives they lived. Who knows? We probably won't be around to see it.