According to the NSW Heritage Office, workers unearthed a series of relics from the Fitzroy Ironworks during the second phase of archaeological monitoring last week.

"The relics include pit floors from former structures at the site such as the rolling mills. Wooden beams used to dampen vibrations from the rolling mills and iron pins were also uncovered," communications and events officer at the NSW Heritage Office Debra Holland said.

Ms Holland said it was still being determined what would happen to the relics, which date from the mid-to-late 1800s.

"Additional discussions with Big W will take place as a matter of priority, to negotiate the best conservation outcome for these relics, based on their heritage significance" Ms Holland said.

"Successful negotiations with Big W has resulted in the retention of significant relics within the pedestrian walkways on the ground level of the proposed car park.

"These significant relics were discovered during archaeological investigations in February 2005 and will form a key part of the interpretation of the site."

The proposed Big W site is of particular historical interest because it is the former site of the Fitzroy Ironworks, Australia's first ironworks commissioned in 1848.

The infrastructure included a Catlan Furnace (1848), Rolling Mills (1859/60 to 1886 and 1896) as well as a Puddling Furnace and possible Engine House (approximately 1865).