St Mary's Cathedral, Sydney

William Wardell drew the spires in the 1860s and Sydney waited until August 2000 to build them. For the whole of the period a camera could record, the cathedral therefore stood with its two western towers cut off flat — the silhouette the city actually knew, and not the one on the postcards now.

It was a building made in instalments, and each instalment took a generation. Fire destroyed the first St Mary's on the night of 29 June 1865, leaving the Pugin façade, the belltower and part of a transept. Wardell, an English Gothic Revivalist who had arrived in the colony in 1858, was commissioned that October. The foundation stone of the present cathedral went down on 8 December 1868, the first completed section was consecrated in September 1882, and the nave and the western towers were not finished until 1928 — in time for the International Eucharistic Congress held in Sydney that September. Then the money ran out and the tops of the towers stayed as they were for another seventy-two years.

So the cathedral is the fixed thing and everything at its feet moves. Frederick Danvers Power stood outside in 1898 as the congregation spilled from the doors onto the roadway and a closed tram went past; men are sitting on the grass bank in the foreground, which tells you as much about a Sydney Sunday as the church does. Sam Hood worked from the south-west in 1937, close enough to catch the rose window, the pinnacled crossing tower and the flat tops together. By the 1951 views the camera has gone up on a roof and the cathedral is one dark mass among a low skyline, a tramway curving past the park below it.

Start at the top of the towers and work down. It is the one part of the building that is not there yet.