Fort Denison, part of the Sydney Harbour National Park, is a protected national park that is a heritage-listed former penal site and defensive facility occupying a small island located north-east of the Royal Botanic Garden and approximately 1 kilometre (0.62 mi) east of the Opera House in Sydney Harbour, New South Wales, Australia. The island is also known as Mattewanye or Muddawahnyuh in the Eora language, and as Pinchgut Island.

Sydney sandstone, also known as the Hawkesbury sandstone, yellowblock, and yellow gold, is a sedimentary rock named after Sydney, and the Hawkesbury River north of Sydney, where this sandstone is particularly common.