Plans for a 1916 Rising exhibition and visitor centre for the GPO have been approved by Dublin City council.
The facility will include a cafe and an outdoor landscaped area.
An Post intends to build the two-storey centre in a courtyard currently not accessible to the public behind the main hall of the O'Connell Street building.
An annotated version of the planning application floor plan.
The development, which is expected to cost around €5m, will involve the construction of a raised courtyard deck with an exhibition area, a gallery space below, and outdoor landscaping.
However, the council has refused permission for a shaded walkway.
The proposed works are not within the historic portion of the GPO and would be confined to the 20th century complex with the entrance to the exhibition area through the main hall.
Councillor Neil Ring said that is one disappointing aspect of the plan.
"We were assured that the main hall of the GPO would be the focal point in terms of the entrance to the exhibition area," he said.