Boulogne-sur-Mer (French: [bulɔɲ syʁ mɛʁ] ⓘ; Picard: Boulonne-su-Mér; Dutch: Bonen; Latin: Gesoriacum or Bononia), often called just Boulogne (UK: /bʊˈlɔɪn/, US: /buːˈloʊn, buːˈlɔɪn/), is a coastal city in Northern France.

Boulogne lies on the Côte d'Opale, a touristic stretch of French coast on the English Channel between Calais and Normandy, and the most visited location in the region after the Lille conurbation.

Both places – and Vindobona (Vienna) – are thought to have derived from native Celtic placenames, with bona possibly meaning "foundation", "citadel", or "granary".

A tall lighthouse was built at Gesoriacum circa 39 AD by order of the Emperor Caligula,[8] possibly in preparation for an invasion of Britain.

Known as the Tour d'Ordre, coastal erosion caused it to topple into the sea in 1644.From the time of Claudius's invasion in AD 43, Gesoriacum formed the major port connecting the rest of the empire to Britain.

His wife founded the city's Notre Dame cathedral, which became a site of pilgrimage from the 12th century onwards, attended by fourteen French kings and five of England.

A culture of smuggling was present in the city until 1659, when French gains in Flanders from the Treaty of the Pyrenees moved the border northwards.

Boulogne received its current status as a subprefecture of the Pas-de-Calais department in 1800 due to the territorial re-organisation in Revolutionary France.

[13][better source needed] The 19th century was a prosperous one for Boulogne, which became a bathing resort for wealthy Parisians after the 1848 completion of the Longueau–Boulogne railway connecting the town with the French capital.

It was closed and cleared on 27 August 1914 when the Allies were forced to fall back ahead of the German advance, but was opened again in October and from that month to the end of the war, Boulogne and Wimereux formed one of the chief hospital areas.

On 22 May 1940 during the Battle of France, two British Guards battalions and some pioneers attempted to defend Boulogne against an attack by the German 2nd Panzer Division.

Despite fierce fighting, the British were overwhelmed and the survivors were evacuated by Royal Navy destroyers while under direct German gunfire.

[15] On 15 June 1944, 297 aircraft (155 Avro Lancasters, 130 Handley Page Halifaxes, and 12 De Havilland Mosquitos) of the Royal Air Force bombed Boulogne harbour to suppress German naval activity following D-Day.

In August 1944 the town was declared a "fortress" by Adolf Hitler but it succumbed to Operation Wellhit, the assault and liberation by the 3rd Canadian Infantry Division in September.

In one incident, a French civilian guided the Canadians to a "secret passage" leading into the walled old town and by-passing the German defenders.

[16] To replace the destroyed urban infrastructure, affordable housing and public facility projects in functional, brutalist building styles were carried out in the 1950s and 60s.

The city is divided into several parts : Boulogne-sur-Mer has an oceanic climate that has chilly winters not far above freezing and cool summers tempered by its exposure to the sea.

[23] It is the oldest building in the upper city of Boulogne, and currently serves as the home to a museum of Celtic remains from the Roman occupation.

The Saint-Louis building of the University of the Côte d'Opale's Boulogne campus opened its doors in 1991, on the site of the former St. Louis Hospital, the front entrance to which remains a predominant architectural feature.

Two health centres are located in Boulogne, the public Hospital Duchenne and the private Clinique de la côte d'opale.

As these collections are exhibited in a medieval castle, one can also discover the Roman walls (in the underground) as well as rooms built in the 13th century (La Barbière, banqueting hall, chapel, covered parapet walk...) La Casa San Martin is currently a museum where José de San Martín the leader of independence struggle in Argentina (also Chile and Peru) died in 1850, from 1930 to 1967 this house was the consulate of Argentina in France.

As an international maritime port on the English Channel (La Manche), the town of Boulogne-sur-Mer has European and American influences in local cuisine.