National Gallery without stopping in. It's like visiting an old friend. And while pausing to say hello to the sculpture by Richard Serra and the painting by Robert Motherwell, we were struck by that other famous quality of the building - the way it invites the visitor's touch.
I. M. Pei's building has always compelled people to touch it, and I'm not sure why. It makes sense in the parts where the whole building comes to a sharp point - you just want to touch that prow, or whatever it is - but throughout the building there are stains on the walls right at the height of a visitor's hand, where countless museum-goers have left a little oily trace of their visit. It's the remarkable gift of this richly complex building that it engages people in such a warmly physical way.
You've got to love a building that makes you want to touch it: