Kiel sits at the head of a long Baltic inlet, the Kieler Förde, at the mouth of the Schwentine and about ninety kilometres north-east of Hamburg. The harbour is deep and stays ice-free, which explains almost everything that happened afterwards. Count Adolf IV of Holstein founded the town in 1233 as Holstenstadt tom Kyle; his son granted it Lübeck city rights nine years later.

It joined the Hanseatic League in 1284 and was thrown out in 1518 for harbouring pirates, which tells you something. Its real institution was the Kieler Umschlag, a fair established in 1431 that became the money and goods market of the whole Duchy of Holstein before fading away around 1850. Duke Christian Albert founded the university in 1665; Max Planck and Hans Geiger both worked there. From 1773 to 1864 the Danish king ruled Kiel in personal union, until the Second Schleswig War took it away and Prussia annexed it in 1867.

On 24 March 1865 King William I moved Prussia's Baltic fleet from Danzig to Kiel. An imperial shipyard followed in 1867, and in 1871 the new German Emperor named Kiel and Wilhelmshaven the empire's war harbours. A town of 18,770 people in 1864 held around 200,000 by 1910.

Then came the canal. Cut from June 1887 and opened by Wilhelm II on 20 June 1895, it runs 98 kilometres from Brunsbüttel on the North Sea to Holtenau on the city's northern edge — a shortcut that let warships pass between two seas without rounding Denmark, and today one of the most heavily used artificial waterways in the world, with something like 32,000 ships a year. It was widened between 1907 and 1914 to take dreadnoughts. The regatta grew up alongside all this: Kiel Week began in 1882 as a race for twenty yachts out of Düsternbrook, the Kaiser started attending in 1889, and by 1894 the newspapers were calling it Kieler Woche.

On 1 November about 250 sailors met at the Union House to ask for their comrades' release. The police shut the building the next day, so the meeting moved outdoors and grew. By 3 November several thousand people were marching behind Karl Artelt and Lothar Popp under a demand for peace and bread — Frieden und Brot. A Lieutenant Steinhäuser ordered his men to fire into them. Seven were killed and twenty-nine badly wounded.

It broke the wrong way for the navy. By the evening of 4 November roughly forty thousand sailors, soldiers and workers held the city. The prisoners walked free, Artelt organised the first soldiers' council, and the council issued fourteen demands covering the prisoners, press freedom, the treatment of crews, and a veto on sending the fleet to sea. Sailors carried the revolt out of Kiel to the other northern ports and beyond. On 9 November the abdication of Wilhelm II was announced and Germany was declared a republic. Within the month every German prince had gone.

Being the navy's city carried a bill, and it came due between 1940 and 1945. Kiel was a fleet base, a U-boat yard and therefore a target. Allied bombing destroyed more than 80 per cent of what remained of the old town, 72 per cent of the central residential districts and 83 per cent of the industrial areas; raids between February and April 1945 finished off a great many U-boats and several major warships in the yards. A British unit under Major Tony Hibbert took the city and the canal on 5 May 1945.

The outer districts came through comparatively intact, which is why Kiel now reads as two places at once: a rebuilt modern centre, and streets of nineteenth-century villas under trees in Düsternbrook and Schreventeich. The state government moved here in 1946 and Kiel was confirmed as capital of Schleswig-Holstein in 1952. In 1947 the city twinned with Coventry.

Kiel Week returns every June, still the largest sailing event in the world — around two thousand boats and some three million people, half regatta and half street festival. Olympic sailing was held in the Bay of Kiel twice, in 1936 and 1972. Out at the fjord mouth stand the Laboe Naval Memorial and U-995, a wartime U-boat you can walk through, which is a strange and useful thing to do in this particular harbour.

The shipbuilding never stopped. Howaldtswerke-Deutsche Werft, founded in 1838, launched Germany's first submarine, the Brandtaucher, in 1850, and still builds them as part of ThyssenKrupp Marine Systems. Alongside a university of 27,000 students sit the Kiel Institute for the World Economy and GEOMAR. In town, the oldest building is the thirteenth-century St Nicholas Church, with Ernst Barlach's Geistkämpfer in front of it, and the 1911 Rathaus has a tower modelled on one in Venice and a paternoster lift that still runs. Across the water, Gaarden is what it always was: the shipyard workers' district.