Sir William Rowan Hamilton was walking through this brisge in Dublin on the 16th October, 1843, when he has one of his wonderful ideas: his quaternions. Nowadays, this very important moment in the History of Mathematics is recorded on a plaque located in the North-West corner of the bottom of the bridge. We can read:
I’ve never been in Dublin yet but I am sure that I am going to visit it very soon… very soon.
Location: Broombridge in Dublin (map)