Where is ‘the biggest pebble in the world’?

The largest single block of stone in the world is in Mount Olga National Park, Northern Territory, Australia. It is Ayers Rock. This huge monolith is over 2.5 km long and rises 348 m above the sand and gravel plains of the Great Plateau. It is oval-shaped and is built of water-worn pebbles of granite cemented by finer sands. Aboriginal tribes regard the rock as of great religious and magical importance, and aboriginal rock carvings and paintings can be seen in shallow caves near its base. The color of the rock varies from mauve to fiery red, depending on the time of day.