The Kugelbake stands in Döse, on the northern edge of Cuxhaven, at the northernmost point of Lower Saxony. This is where the Elbe stops being a river. The estuary measures roughly eighteen kilometres across here, and by the convention that mariners and geographers both accept, the North Sea begins at this line. In nautical terms the beacon marks the join between the Lower Elbe and the Outer Elbe; it also serves as the symbolic divide between the Elbe and Weser estuaries. The structure itself is about thirty metres of open timber framework, standing 29.63 metres above mean high water — a lattice you can see straight through, which is precisely the point, since a solid tower of that size would not survive a single winter here. In the Low German of the Middle Ages, a bake was any navigational aid at all, lighthouses included. Kugel means ball.

Wood, salt water, and North Sea storm surges make a short partnership. The first Kugelbake lasted only a few decades, and the pattern set early: reconstruction roughly every thirty years, the first of them around 1737. In 1782 a causeway made the beacon permanently reachable on foot rather than only at low water. In 1867 the whole structure was reset on granite blocks to a design by the architect Hugo Lentz, an attempt to give the timber something more durable to stand on than shifting sand. None of it stopped the cycle. The Kugelbake visible today was raised after 1945, which makes the current tower younger than most of the people who grew up looking at it — and older than nothing much except the last storm.

In 1853 the beacon was lit at night for the first time, the light nothing more elaborate than a fire burning inside a small hut set within the frame. Ships needed it: the channel bends awkwardly here, and the bend is hardest to read in the dark. The light's career was short and repeatedly interrupted. When the Franco-Prussian War broke out in 1870, it was dimmed deliberately, on the theory that a confused enemy navigator was worth more than a safe neutral one. By 1878 a lightvessel stationed in the channel year-round had reduced the Kugelbake's lamp to a reserve. In the First World War the light was removed altogether, for the same reason it had been dimmed in 1870. The rebuild of 1924 came back without the eponymous ball: in its place went two round discs, mounted at right angles to one another, reading as a sphere from a distance and offering the wind far less to push against.

Through the winter of 1899 and into 1900, the physicist Jonathan Zenneck used the Kugelbake for something its builders had never imagined. A wooden hut went up inside the frame, filled with antennas and apparatus, and from it Zenneck worked at sending messages between the mainland and ships at sea. What he assembled there became the first coastal radio station in Germany. It is a fitting piece of history for the structure: a navigational aid whose whole existence depended on being seen, briefly repurposed to prove that ships could be reached without anyone seeing anything at all.

Cuxhaven put the Kugelbake on its coat of arms in 1913, and the silhouette has been doing municipal duty ever since — on letterheads, on souvenirs, on the sign that greets drivers coming into town. Its working life ended more quietly. In 2001 the federal waterways administration handed the beacon to the agency that manages historic federal property, an admission that the thing no longer served any navigational purpose. A foundation was set up to keep it standing, and since 2002 the Kugelbake has belonged to the city itself, protected as a monument. It is illuminated at night now, which it had not reliably been for a century. The light is for visitors. No one out on the Elbe is steering by it any more.