June 3, 2008 update:
The pattern has been re-written to add more room at the top of the heel flap, making it easier to pull the sock over your heel. There are more gusset increases, the heel flap is wider, and there are more cuff sts which are worked in a rib up the center back.
Please visit the link above and download the most recent version of the pattern.
This sock gets its name from the arch of twisted stitches at the top of the pattern motif which reminds me of the Sydney Opera House. The 1x1 rib in the diamond motifs slopes towards a line of double decreases in the center and the diamonds are separated by yarn overs.
Sydney is worked toe-up, beginning with a provisional cast on and a short row toe. The unique gusset and slip stitch heel flap construction does not require picking up stitches, and the sewn cast off provides a neat finish with plenty of stretch.
If you have questions or comments, please feel free to send me an email.