The firing of the One o’clock Gun dates back to 1861 when it allowed ships in the Firth of Forth to set the maritime clocks they needed to navigate the world’s oceans.
The idea was brought to Edinburgh from Paris by businessman John Hewitt.
The gun is fired at 1pm every day except Sundays, Christmas Day or Good Friday, with crowds gathering to enjoy the spectacle.
The first gun was a 64-pounder, but since 2001 a 105mm field gun has been fired from the Mills Mount Battery.
This famous time signal is located just outside the Redcoat Café. Passing through the Portcullis Gate, it's on the right at the far end of the Argyll Battery.