Ultimo and Pyrmont: Then and Now
That's the Powerhouse Museum, located between Pyrmont and Ultimo. If you could hover above it in a helicopter, the view would look something like this:
Imagine if you could magically click a link and jump back in time, and see the same view from sometime between 1900 and 1939...
If you're lost: in the older picture, look beyond the chimneystack, and just to the left. Immediately beyond the chimney is a vacant block of land; at the top end of this is a short road, which has on the right a not-quite-right-angle corner. The road then continues up the picture - but it's not quite straight, it bends a little to the right. If you look at the modern picture, you can see the same not-quite-right-angle corner and the same not-quite-straight road - although now the Western Distributor flys across the not-quite-straight road.
See the large building inside the block bounded by the not-quite-straight road? That building is Global Switch Sydney - built in the last days of "Build it and they will come". It's only in the last few years that it's starting to reach full capacity.
The railway line visible in the earlier picture was the Darling Harbour Goods line, which formed the first part of the Metropolitan Goods Railway Line. It's now used as the Metro Light Rail line.