The convent of the Sisters of Mercy took 16 years to build and opened on August 8, 1909, with an afternoon tea and performances from the town band.

History will be repeated on Saturday when, 100 years later, the 2009 Singleton Town Band performs and guests have tea and scones in the grounds of the magnificent building.

Ten sisters of Mercy arrived in Singleton in 1875 and carried out the works of primary and secondary education in the town, care of orphans and visiting the sick.

There were 108 sisters in the Hunter Valley at the time the convent opened. Today there are nine.

The first wing of the convent comprised a large school room and a music room and dormitory space on the second level. Eventually nearby St Catherine's College was built and opened in 1911.

Newcastle architect Frederick Menkins designed the main portion of the convent.

The building features cedar woodwork throughout, high ornate pressed metal ceilings, ornate timber staircases and original furniture. The convent is also home to many historically significant documents and journals relating to the immigration of the Sisters of Mercy from Ireland.

Sister Faith Jones of the Sisters of Mercy based at Tighes Hill, said the size of the convent reflected the vision of the order's founding women.

"It would become the place of training for those who entered the community as well as the annual place for holiday and retreat for all the sisters who had gone to other parts of the Hunter Valley," Sister Faith said.

The centenary celebrations will start at 2pm on Saturday with a prayer ceremony led by Bishop Michael Malone.