Cleopatra's Needle, on the north bank of the Thames in London.

I have more information on the needle's history somewhere - I'll dig it out and put it here. What I can remember: it's genuinely ancient Egyptian, I think from Heliopolis, it was lost in the sands near Alexandria for a couple of thousand years, it was brought to England in the early 1800s, six people died getting it here, and it has a twin in Central Park, New York.