Australia's capital city, Canberra, is built on what geological landmark?

The geology of the Australian Capital Territory in which Canberra lies includes rocks dating from both the Ordovician and Silurian periods. During the Ordovician period some 480 million years ago, much of eastern Australia where Canberra was built, was part of the ocean floor.

The early European name for the district was "Limestone Plains". In 1820, Governor Lachlan Macquarie, the Governor of New South Wales sent a party to discover the Murrumbidgee River which flows through what is now the Australian Capital Territory. The party was provided with acid to test for limestone.

Surprisingly enough, there is little limestone evident on the surface in the district except for a rocky limestone outcrop near the Museum of Australia on Lake Burley Griffin which geologists say is the result of when the ocean floor was raised by major volcanic activity in the Devonian period which formed much of the eastern coast of Australia.