The St Helena Penal Establishment was situated on a small Island in Moreton Bay, some 5 km from the mouth of the Brisbane River, covered approximately 88 hectares above the high water line and was one of the loveliest islands in the bay. The elevated tableland on which the prison was built looked like a large rugged block of ruby and emerald rising out of the sea. Its steep chocolate brown patches of rich soil, bordered with green fields of cultivation and bases of grass and shimmering sand provided a striking first picture of the island. It has had a fascinating history from the time it was first discovered; but its most important period began when it became a high-security colonial prison in 1867. The overcrowding of Brisbane's gaols resulted in the conversion of buildings originally intended for a quarantine station on St. Helena Island, into accommodations for prisoners convicted for a wide variety of crimes.