The area that is now the Dolomites was once a tropical sea. The geology tells the story of rising and falling sea levels over tens of millions of years: immense coral reefs grew up surrounded by water that could be more than a thousand metres deep. Huge volcanic eruptions caused the reefs to fossilise, only to give way to further layers of coral. Along with the corals, the bones of sea creatures formed in layer after layer on the sea bed, creating deep beds of limestone. 

The mountains were formed as the Europe and Africa crushed together, forming the Alps, then sculpted by glaciers and rivers, and the wind for couple of hundred million years.

The Dolomites get their name from Déodat de Gratet de Dolomieu (1750-1801), who, on his way to Rome, spotted rocks, that turned out to contain a previ­ously-unknown mineral — double calcium magnesium carbonate, CaMg(CO₃₎2. The rock, and the mountains, came to be named after him.

Map from dolomitiunesco.info.

Nine areas of the Dolomites have been listed by UNESCO as a World Heritage site. According to UNESCO:

The nine components of The Dolomites World Heritage property protect a series of highly distinctive mountain landscapes that are of excep­tional natural beauty. Their dramatic vertical and pale coloured peaks in a variety of distinctive sculp­tural forms is extraordinary in a global context. This property also contains an inter­na­tionally important combin­ation of earth science values. The quantity and concen­tration of highly varied limestone forma­tions is extraordinary in a global context, whilst the superbly exposed geology provides an insight into the recovery of marine life in the Triassic period, after the greatest extinction event recorded in the history of life on Earth. The sublime, monumental and colourful landscapes of the Dolomites have also long attracted hosts of travellers and a history of scientific and artistic inter­pret­a­tions of its values.

[…]

Criterion (viii): The Dolomites are of inter­na­tional signi­ficance for geomor­phology, as the classic site for the devel­opment of mountains in dolomitic limestone. The area presents a wide range of landforms related to erosion, tectonism and glaci­ation. The quantity and concen­tration of extremely varied limestone forma­tions is extraordinary in a global context, including peaks, towers, pinnacles and some of the highest vertical rock walls in the world. The geolo­gical values are also of inter­na­tional signi­ficance, notably the evidence of Mesozoic carbonate platforms, or “fossilized atolls”, partic­u­larly in terms of the evidence they provide of the evolution of the bio-constructors after the Permian/Triassic boundary, and the preser­vation of the relation­ships between the reefs they constructed and their surrounding basins. The Dolomites also include several inter­na­tionally important type sections for the strati­graphy of the Triassic Period. The scientific values of the property are also supported by the evidence of a long history of study and recog­nition at the inter­na­tional level. Taken together, the combin­ation of geomor­pho­lo­gical and geolo­gical values creates a property of global significance.

UNESCO: The Dolomites

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For more about the Dolomites see: dolomitiunesco.info.