The Ruskin Library's archive of watercolours, books and manuscripts is open to scholars - there is a little reading room at the far end of the building - but there is also a public gallery, wrapping round that mysterious inner Ruskinian casket and passing through it via a glass bridge. The opening exhibition, Ruskin and the Lake District, puts the old dilettante (somehow he never seemed young) into the context of the area. It is the building that visitors will appreciate the most - I find a few Ruskin watercolours go a very long way. Here there is a problem in that - like the British Museum where the old British Library was off-limits for most visitors - there are large portions of this small building that only initiates may enter. Still, it is designed so that you can get a feel for the secret spaces and even glance into them and down on them from certain vantage points.

The casual visitor may not necessarily appreciate that the black curving interior walls that meet you on entering represent the dock walls of Venice. Or that the gentle upwards slope of the floor, moving from transparent to solid, represents the transition from water to dry land, or any of the other metaphorical details that MacCormac attempts. Nor can this strictly symmetrical building convey much of a sense of what is called "Ruskinian Gothic", the architectural style for which he was responsible, even though MacCormac claims that it is "gothic in mood".

This does not really matter. MacCormac's Ruskin Library is suitably enigmatic. It captures the distinct weirdness and sadness of the man. And - like its grandaddy, the British Library, which is also Victorian in feel - it is impossible to understand until you experience the richness of the interior. It is concentrated architecture of a very high order.