Tough at the top

The clocks on Big Ben were cleaned by abseiling window-cleaners. Some other big cleaning/painting jobs:
— Repainting the Forth Railway Bridge used to be a metaphor for never-ending work, but a new coating completed in 2012 is estimated to have a life of 25 years.
— Sydney Harbour Bridge was, for the first 80 years of its life, cleaned by hand, but last year it was done for the first time by robot.