The massive cube of the exterior of Ledoux’s Besançon Theatre, against which an unpedimented Ionic portico is set, can already be found, however, at his Château de Benouville begun in 1768; the later edifice is nevertheless much more rigidly cubical and much plainer in the treatment of the rare openings. In the interior Ledoux substituted for a Baroque horseshoe with tiers of boxes a hemicycle[14] with rising banks of seats and a continuous Greek Doric colonnade around the rear fronting the gallery. The extant constructions at Arc-et-Senans are less geometrical; instead of Greek orders there is much rustication and also various Piranesian touches of visual drama. It was this commission which set Ledoux to designing his ‘Ville Idéale de Chaux’; that was his greatest achievement, even though it never came even to partial execution, nor could perhaps have been expected to do so, so cosmic was the basic concept. The _barrières_ varied very widely in character; some were very Classical, others in a modest Italianate vernacular; some were rather Piranesian in their bold rustication, the Besançon Theatre. The most significant, however, were notable for the crisp and rigid geometry of their flat-surfaced masses. The extant Barrière de St Martin in the Place de Stalingrad in the La Villette district of Paris consists of a tall cylinder rising out of a very low, square block; this is intersected by a cruciform element projecting as three pedimented porticoes beyond the edges of the square (Plate 2A). Although the range of Ledoux’s restricted detail here is not very great, it is varied to the point of inconsistency all the same. The rather heavy piers of the porticoes are square, with capitals simplified from the Grecian Doric; yet around the cylinder extends an open arcade of Italian character carried on delicate coupled columns.