Cabot Square is awash with city workers any time the sun is out. It's fountain is a popular spot for tourists too, who like to get a photo with the Canary Wharf tower imposingly behind them.
The cache is a magnetic fresh-breath strip container (sorry!), and IT IS NOT ATTACHED TO THE RAILINGS! Please leave it high enough up so it doesn't get wet, but low enough to be hidden.
Be sure to look up at these buildings when you get there and take in the imposing structures.
Have fun!