Tucked away in a dimly lit room in the Natural History Museum (NHM), Systema Metropolis is an installation that, on its surface, follows the method of scientific classifications, and its Latin title perpetuates this.

Dion and his assistants made field trips to four notable London locations: the site of the Olympic Park in east London; the Thames at Battersea; the Victorian cemeteries of Highgate, Brompton and East Finchley, resting places to Karl Marx, Thomas Huxley and Emmeline Pankhurst; and a stretch of the A40.

They took samples from the soil and water; they identified flora in each location and logged the fauna they encountered. They recovered, with the same painstaking gentleness with which an archaeologist might excavate a precious statue, turfs, plastic ducks, gumboots, old footballs and beer cans and, from the river, at least one battered fluffy thing. These artefacts, alongside ones from the NHM's own storerooms - busts of Linnaeus, books (including Linnaeus's Systema Naturae), preserved specimens, trowels, butterfly nets and other paraphernalia of fieldwork - make up Systema Metropolis.

But Dion is also interested in the active process by which he builds his collection, not simply its end result. This is a display that, like an answer to an algebraic equation, shows its working. The ducks and flattened footballs appear in a polytunnel and one peers through the translucent plastic to look at the tatty tennis balls, rusted aerosols and jars with snakes and eels. There are videos of the team working on their various digs, shaking insects from nets into bags. In the centre of the installation, there is the electric car in which Dion drove stretches of the A40.

There's undoubtedly a whimsical element at work, but as in the Borges story, it's a quality that leads us to a new realm of questioning. As an artist whose prolific work includes excavations on the site of New York's Museum of Modern Art, constructing cabinets of curiosities as well as numerous projects relating to the natural world, Dion's elaborate fictions require us to consider our present state as well as our past and future.

Louise Gray is a freelance arts journalist

Systema Metropolis is at the Natural History Museum, London, until 2 September 2007, www.nhm.ac.uk/mark-dion