Little brothers

Just back from a weekend visiting Reims and Laon - two fantastic Gothic cathedrals.

What's interesting is that each has a 'little brother'.

At Reims, Saint Jacques has just the same three storey elevation to the cathedral. But it's dumpy instead of breathtakingly tall, and that ruins the proportions.

At Laon, the former abbey church of Saint-Martin has two towers that aim at transparency in the same way as the towers of the cathedral. It doesn't quite manage the amazing lightness of construction though - the towers just look as if the windows were made too big.

It's interesting to see these 'little brothers', even though they're not great works of architecture. It's easy to walk into a cathedral like Laon and take it for granted. When you see Saint-Martin, you realise just how revolutionary, just how amazingly original and complex, was the cathedral mason's vision.

And I think, rich as Reims is, Laon is probably my favourite Gothic cathedral in France. It's full of light, spacious, transparent. It has the famous sixteen oxen that sit at the top of the towers, commemorating a miraculous ox that appeared when those pulling the blocks of stone up the hill to the cathedral couldn't manage.

And the towers have a secret. From below you can already see how complex is the design, with an octagonal top stage on top of a square tower, and square transparent turrets angled out from the octagon. But if you climb the towers (the local tourist office arranges ascents occasionally, and we were lucky) you'll see that the mason included a transparent round spiral staircase within one of those square turrets, creating yet another layer of complexity.

Laon is one of the earliest of the Gothic cathedrals. And yet here is a complete vision - a mason who knew exactly what he wanted, how to manage space and light, how to manage geometry.

And in the middle of the nave is his other secret - the shiny black stone which gave him all his measurements, a lozenge divided into rectangles whose measurements reflect the Golden Section. There must have been such stones in many other churches but I'm not aware of others surviving. And it's in roughly the same place as the maze at Chartres, which can in one sense be interpreted as a builder's claim on our memory (Daedalus, who made the original Cretan labyrinth, was the first of architects).