The island lies approximately one kilometre (one-half nautical mile) off France's north-western coast, at the mouth of the Couesnon River near Avranches and is 7 hectares (17 acres) in area.

As sea levels rose, erosion reshaped the coastal landscape, and several outcrops of granite emerged in the bay, having resisted the wear and tear of the ocean better than the surrounding rocks.

Mont-Saint-Michel consists of leucogranite which solidified from an underground intrusion of molten magma about 525 million years ago, during the Cambrian period, as one of the younger parts of the Mancellian granitic batholith.

Popularly nicknamed "St. Michael in peril of the sea" by medieval pilgrims making their way across the flats, the mount can still pose dangers for visitors who avoid the causeway and attempt the hazardous walk across the sands from the neighbouring coast.

The well-flavoured meat that results from the diet of the sheep in the pré salé (salt meadow) makes agneau de pré-salé ('salt-meadow / salt-marsh lamb'), a local specialty that may be found on the menus of restaurants that depend on income from the many visitors to the mount.

The coastal flats have been polderised to create pastureland, decreasing the distance between the shore and the island, and the Couesnon river has been canalised, reducing the dispersion of the flow of water.

The new bridge was completely submerged on 21 March 2015 by the highest sea level, a once-in-18-years occurrence, as crowds gathered to snap photos.

[17] Unable to defend his kingdom against the assaults of the Vikings, the king of the Franks agreed to grant the Cotentin Peninsula and the Avranchin, including Mont-Saint-Michel traditionally linked to the city of Avranches, to the Bretons in the Treaty of Compiègne.

Around 989–990 these traditional bishoprics, dependent of the archbishopric of Rouen and that had been left vacant during the time of the Viking raids, regained their bishops.

This he rewarded with properties and grounds on the English side of the Channel, including a small island off the southwestern coast of Cornwall which was modelled after Mont-Saint-Michel and became a Norman priory named St Michael's Mount of Penzance.

[citation needed] During the Hundred Years' War, English forces unsuccessfully besieged Mont-Saint-Michel (which was under French control) twice.

[citation needed] The wealth and influence of the abbey extended to many daughter foundations, including St Michael's Mount in Cornwall.

From then on Corroyer, a member of the Academy of Fine Arts, devoted fifteen years of his life to the restoration of "la Merveille".

[citation needed] During the occupation of France in World War II, German soldiers occupied Mont-Saint-Michel, where they used St. Aubert church as a lookout post.

After the Allies' initial D-Day invasion of Normandy that began on June 6, 1944, many exhausted German soldiers retreated to strongholds like Mont-Saint-Michel.

On August 1, 1944, a single American soldier – Private Freeman Brougher of Pennsylvania and the 72nd Publicity Service Battalion – reached and liberated Mont-Saint-Michel accompanied by two British reporters, Gault MacGowan of the New York Sun and Paul Holt with the London Daily Express.

Robert de Thorigny, a great supporter of Henry II of England, who was also Duke of Normandy, reinforced the structure of the buildings and built the main façade of the church in the 12th century.

Horrified by the cruelty of his Breton ally, Philip Augustus offered Abbot Jordan a grant for the reconstruction of the abbey in the new Gothic architectural style.

[23] Charles VI is credited with adding major fortifications to the abbey-mount, building towers, successive courtyards, and strengthening the ramparts.

[27] The community meets four times a day to recite the liturgical office in the abbey, or in the crypt of Notre-Dame des Trente Cierges in winter.

[9] The main institutions are shared by: Overtourism is a problem for Mont-Saint-Michel, exacerbated by tourists mostly visiting on day-trips, which causes overcrowding from 10:00 to 16:00, especially in the summer.

Ten hiking trails have been created that enable pilgrims from various European countries to retrace the path their ancestors may have taken during a medieval pilgrimage.

[33] Part of the action in Helen MacInnes's 1943 film thriller Assignment in Brittany takes place at the Mont, including a dramatic nighttime chase across the sands.

Peter Jackson is said to have taken inspiration from Mont-Saint-Michel in designing Gondor's capital city, Minas Tirith, in his 2003 film The Lord of the Rings: The Return of the King.

The climax of the 2016 young adult novel The Inquisitor's Tale takes place in and around Mont-Saint-Michel, as the protagonists race over the causeway to the Abbey, pursued by the King's men.