From Poetry Wiki
A monolith is a geological or technological feature such as a mountain, consisting of a single massive stone or rock. Erosion usually exposes these formations, which are most often made of very hard and solid metamorphic rock.
The three largest on Earth are currently:
- Mount Augustus, in Western Australia 
- La Peña de Bernal, in Mexico
- Stone Mountain, in Stone Mountain Park, Stone Mountain, a suburb of Atlanta, Georgia, USA
Note: For many years, Uluru/Ayers Rock was listed in record books as the world's largest monolith. This is wrong on two counts. Uluru is not a monolith at all, but even if it were, Mt Augustus is about 2.5 times its size.
- Beacon Rock, Columbia River Gorge, Washington
- Bottleneck Peak and Moon, Sids Mountain, Utah
- Devils Tower National Monument, Wyoming
- El Capitan, Yosemite National Park, California
- Enchanted Rock, Llano County, Texas
- Haystack Rock, Clatsop County, Oregon
- Looking Glass Rock, Transylvania County, North Carolina
- Stawamus Chief, Squamish, British Columbia, Canada
- Stone Mountain, Stone Mountain, Georgia
- Frau Holle Stone, near Fulda, Germany
- Humber Stone, Humberstone, near Leicester, England.
- King Arthur's Stone (Cornwall)
- Logan Stone (Trereen, Cornwall)
- Odin Stone (Stenhouse, Orkney; destroyed in 1814)
- Rock of Gibraltar
- Mount Coolum, Queensland
- Mount Wudinna, near Wudinna, South Australia
- Mount Augustus, Western Australia
Many of these have legends attached.
- Top stone on the Mausoleum of Theoderik, Ravenna
- Aztec calendar "Stone of the Sun"
- Rune stones
- Obelisks - see this article for a list
- Ogham Stone, Dingle Peninsula, Ireland
- Adam and Eve Stones, Avebury, Wiltshire, England
- Merlin Stone, Avebury Stone Circle, Wiltshire, England
- Manzanar National Historic Landmark, USA
The best-known cultural reference is to the Monolith from the Space Odyssey science fiction series by Arthur C. Clarke and Stanley Kubrick. In the series, the Monoliths are black ebon and transparent oblong slabs, fitting exactly into the ratio 1:4:9 (9 height, 4 width and 1 depth). They form part of a Solar-System-wide computer network planted by an alien civilization to monitor an experiment which culminated in humanity.