The Kaiser-Wilhelm-Kanal — today the Kiel Canal — was cut across Schleswig-Holstein between 1887 and 1895, slicing through the Neumünster–Flensburg railway, which crossed on two parallel swing bridges. In 1907 the decision to enlarge the canal came with a mandate to clear away its obstacles, and the Rendsburg crossing was the worst of them. The engineer Friedrich Voss (1872–1953) was handed a brutal pair of constraints: clear the water by 42 metres, and never let the track climb more steeply than one in a hundred and fifty. The rails at the crossing sat about seven metres above the canal. They needed to rise some thirty-six. At that gradient the climb takes kilometres, and Rendsburg did not have kilometres to spare.

Voss's answer looks, on a map, like a drafting error. North of the canal the line swings into a complete 360-degree loop roughly four and a half kilometres long, curling around the edge of Rendsburg and gaining height the whole way before straightening out to cross the water. The district enclosed by the curve is simply called Schleife — the loop. Rendsburg station sits at ground level near the foot of the spiral, so a train can call there and then spend the next several minutes climbing above the rooftops it has just left, passing over streets it rolled through a moment earlier. Passengers who do not know the geometry spend that stretch quietly convinced the driver has taken a wrong turn.

Construction ran from 1911 to 1913. The contractors C. H. Jucho and the Gutehoffnungshütte assembled roughly 17,740 tonnes of steel with something on the order of 3.2 million rivets, at a cost of 13.4 million gold marks. The main cantilever span reaches 140 metres across the shipping channel; the structure stands 68 metres at its highest point. Seven workers died building it. The finished bridge is federal property, run by the same waterways administration that owns the canal beneath it, and it carries a heritage-monument listing — which in Schleswig-Holstein is about the highest compliment available to a piece of working infrastructure.

Suspended from the main span on twelve cables is the reason people photograph this bridge rather than merely ride across it: a transporter-bridge gondola, one of a small handful still operating anywhere in the world. It runs a 125-metre traverse in a little under two minutes, six metres above the water, carrying up to four cars and a hundred people on foot or on bicycles, quarter-hourly from five in the morning until eleven at night, free of charge. Through the 2010s it averaged around 520 vehicles and 1,700 people a day. It is not a heritage attraction that happens to move. It is how one bank of Rendsburg gets to the other.

On 8 January 2016, at about 6:40 a.m., the general cargo ship Evert Prahm struck the gondola. Two of the twelve suspension cables parted. The ferryman and his single passenger were injured. On 15 March the gondola was taken down and moved to a shipyard for assessment, and the assessment was that it could not be repaired. Rendsburg went without its crossing for six years. Construction of a replacement began in April 2020, the first test run came on 18 November 2021, and service officially resumed on 4 March 2022. The new car — 15.5 metres long, 10 metres wide, 45 tonnes, around eleven million euros — was deliberately built to resemble the one it replaced, modern machinery inside an old silhouette.

The wrecked gondola was headed for scrap. In the summer of 2024 a Rendsburg businessman, Martin Sick, bought it instead, and it now sits on the canal bank within sight of its successor, kept as a landmark and converted for a restaurant and cultural events — the first of them around the SH Netz Cup in the summer of 2025. So the town has two of them now. One still swings across the channel every fifteen minutes with four cars and a queue of cyclists aboard. The other rests on the grass beside the water it used to cross, close enough to watch the replacement do the job it did for a hundred and three years.