The GPO was the ground zero of the Rising, first occupied by the rebels shortly after noon on Easter Monday 1916, and held until Friday evening.
Over the course of four days the building served as the headquarters of the uprising, with rebels also occupying the adjacent Metropole Hotel (the ruins of which are pictured above) and the Imperial Hotel.
On Wednesday, British troops opened fire on the building with small arms and eventually artillery.
The following day rebels from Henry Street retreated into the building, while James Connolly was treated there for a gunshot wounds.
The shelling continued on Friday with much of the building now heavily damaged or on fire.
At 6.15pm on Friday part of the roof collapsed. The rebels then evacuated the GPO under fire, moving to Moore Street.