Walking through the quad of the Arts & crafts centre in Christchurch - if it's a weekend there's a market - you look up and there is a doorway and a staircase in the sky. Look behind you and there's a doorway and stairs up to the great hall (the Canterbury society semms to have done their best to recreate an Oxbridge college in the sun); the doorway in the sky is a pared-down version of the style.
Walk a little further and turn round and you're inside the doorway looking out. It's all perspective!
(I'm finally uploading the images from my trip to New Zealand in 2004, spurred on my illustrating my diary to give to my mum; you'll find them at http://www.flickr.com/photos/marypcb/ - it will take a while to get them all uploaded though!).