Cottbus is one of the cultural centres of the Sorbs, the Slavic minority whose ancestors settled Lusatia long before Brandenburg existed as a margraviate, and whose language has clung on here through a thousand years of German rule. The city name itself is Sorbian, usually traced to a form recorded as Chotibuz - by one traditional reading, something close to "pretty little houses." That heritage is not a museum piece. Lower Sorbian appears alongside German on signage in the city, and the surrounding villages of the Spreewald remain the core of the language's shrinking territory. Twenty kilometres west, at Slawenburg Raddusch, a full-scale reconstruction of a ring fortress shows how the Lusizi - the Sorbs' ancestors - fortified this marshy country a thousand years ago. It is a strange thing to stand in a German city of a hundred thousand people and realise you are in a Slavic capital.

Ask what Cottbus was historically famous for and you get three answers: cloth, grain and beer, and Baumkuchen - "tree cake," a cylindrical layer cake baked on a rotating spit until its cross-section shows rings like a felled trunk. The cloth mattered most. From around 1860 the industrial revolution arrived in force; the town's first clothmaking factory and first military barracks went up in the same era. The transformation was sealed in 1865, when the Berlin-Görlitz railway was routed through Cottbus, wiring the town into the empire's freight network and linking it to the mill towns of Guben and Forst and onward to Wrocław. Prosperity brought institutions with it. In 1885 Dr. Carl Thiem, considered the father of trauma surgery in Germany, opened a private clinic here that still operates today; the first telephone system followed in 1886, and a public textile college was founded after the three largest German carpet manufacturers merged.

Money that arrives suddenly wants somewhere to be seen spending itself, and in 1908 Cottbus got the Staatstheater - a jewel-box Art Nouveau house designed by Bernhard Sehring, the architect behind Berlin's Theater des Westens. The exterior is handsome; the interior is the point, all sinuous plasterwork and flowing ornament from the brief moment when Jugendstil ran through German design like a fever. Around it, the well-preserved medieval core and the 19th-century districts that grew up during the textile boom give the centre an unexpected density of good buildings, threaded with parks that have earned Cottbus a reputation as a green city. On the eastern edge lies Branitz, the landscape park that Prince Hermann von Pückler-Muskau shaped in his old age and where an earth pyramid rising from a lake serves as his grave - a story in its own right.

The population arc tells the region's history without needing a single adjective. Cottbus first passed 100,000 residents in the 1970s - the threshold at which German bureaucracy grants a town the title Großstadt - and peaked above 130,000 in the East German years, when the mines and the plants and the barracks all needed hands. After reunification the hands were no longer needed. Unemployment rose, the young left for Munich and Hamburg and Berlin, and by 2019 the city was back down to around 100,000, hovering at the edge of losing its designation. It has not lost it. The population is rising again, part of a Germany-wide drift back into cities, helped by the ninety minutes of track between here and Berlin. The Soviet-era prefab suburbs are being steadily refurbished, and on weekend nights the town centre belongs to whoever has just watched FC Energie Cottbus play.

North of the city the Spree loses its nerve and splits into hundreds of channels, and the result is the Spreewald - a waterlogged forest of alder and meadow navigated by flat-bottomed punts, where villages are reached by bridge or by boat. Burg lies about 15 km north-west and serves as the southern gateway. Closer in, the Spreeaue reserve protects 160 hectares along the river's course, laced with the cycle paths that fan out from Cottbus in every direction across country flat enough to make a beginner feel strong. The best introduction to all of it is the Saturday market on Oberkirchplatz, which opens at seven and packs up by midday: Spreewald growers selling their own produce, gherkins above all, the crop this marsh has been famous for since long before anyone dug for coal.