The building work on La Sagrada Familia was restarted several years ago. It's a strange thing, walking round a cathedral that is a building site, when you are more used to ones that have been crumbling for over 500 years. Standing under the open sky, between the giant spires that lean across you, it's a shock to think of the scale of a religious building in this era. (Though perhaps it's being finished now because of its architect, not its original purpose.)

It's a glorious structure, one that causes vertigo from the ground, or from the lofty, delicate walkways between the spires. It's a crazy jumble of details, from the doorway arch covered with hundred of little enthroned saints, to the pillars sitting on giant turtles, to the way that the stones look melting candlewax from a distance. The level of detail is astonishing. It's a giant treasure box.

It's fantastically ugly, and astonishingly beautiful. If you go down into the crypt you can see the model made for the monastery that he designed outside Barcelona, using bags of sand and string to work out the loads and angles for the arches, showing his unique approach to architecture.