The harbours — first and foremost those of Hamburg and Bremen — remain major transshipment terminals today, even as everything around them constantly changes. Sometimes the harbour had to follow the river when the riverbed shifted, as at the inland port of Duisburg-Ruhrort, where the Ruhr meets the Rhine.

The Romans used the Rhine, Germany’s most important river, to advance northward, swiftly founding Xanten in the Lower Rhine region — a city that for a time was the largest north of the Alps.

In the Archaeological Park of Xanten, on the western edge of the Lower Rhine region, a few magnificent Roman buildings have been reconstructed. From Xanten, the Romans ventured further into the unknown. Opposite Xanten, on the far bank of the Rhine, legionaries travelled along the River Lippe and pushed northward through the virgin forests of Westphalia. Today, Bochum-based aerial archaeologist Bao Song is searching for the remains of Roman camps along the northern border of the Ruhr region — and for the camp where the Roman general Varus and his defeated legions took shelter after their catastrophic defeat at the hands of Arminius.

The Rhine has been Germany’s cultural axis for 2,000 years. The castles of the Middle Rhine — from Katz to Maus — are today a UNESCO World Heritage Site. Perched on the steep Rhine cliffs, they speak of power and architectural mastery, and have been visible since ancient times to travellers passing from one customs post to the next along the river.

Today, huge industrial plants line the river: from the chemical giant BASF to Industriepark Höchst to Bayer, alongside vast power stations that draw water from the Rhine to cool their systems before discharging it, significantly warmed, back into the river.

Yet other rivers besides the Rhine and its tributaries the Neckar, Main and Ruhr also shape the country. From above, time seems to stand still along the Elbe. Nowhere else in Germany do water birds have so much space as in the meadows of the Elbe valley, where at the end of summer young storks prepare for their first migration south — without their parents.

Heligoland, Germany’s only open-sea island, is so welcoming to its resident seals that they give birth on the beaches of the dune island every Christmas. In summer, guillemots nest on the sea stack known as Lange Anna. Along the East Frisian coast, at the island of Juist, workers from the seal rescue station release their rehabilitated pups at Norddeich. From the air, you realise that saying goodbye can be truly hard — for seals and humans alike.