Tank Stream

The current site of the General Post Office is situated over the now entirely enclosed Tank Stream, which was once the primary source of fresh water for the Penal Colony of New South Wales, shortly after the arrival the First Fleet on 26 January 1788, under the direction of Arthur Philip, the First Governor.

Source: Wikipedia

The GPO Grand group who manages the restaurants within the GPO building has always maintained and allowed public access to the lower ground floor of the building so people can view the tank stream in accordance with the heritage management plan.