ARCHITECTS, as befits their profession, are usually less than keen to be associated with ruins.

Their designs are usually sunny affairs, showing an unlikely amount of trees and a happy family around an excitingly angular new building.

The current exhibition at Cardiff's National Museum and Gallery, Piranesi's Sublime Dreams, left, shows this was not always the case.

Architect and artist Giovanni Battista Piranesi was born in 1720, moved to Rome in 1740 and never looked back.

He devoted his entire career to the splendour of ancient and modern Rome, and the Imaginary Prisons series appearing in the gallery documents a possible future.

First published in 1749 as a set of fourteen prints, these visions of ruined grandeur present an ideal of a city almost unsullied by inhabitants.

The black-and-white severity of the prints have inspired writers down the centuries including Coleridge, Edgar Allen Poe and Huxley.

The concept of the justice of ancient Rome carried to an extreme gave him the freedom to invent vast and imposing architectural structures.

Imaginary Prisons was essentially a private work and Piranesi had doubts about presenting it to the public.

But two hundred and fifty years later, these complex visions of a city where man was just another moving part still have the power to enthrall.

The exhibition, borrowed from Manchester's Whitworth Art Gallery, runs until June 4 at the National Museum and Gallery, Cathays Park, Cardiff.

The museum is open from 10am until 5pm every day except Monday and admission is free.