Copenhagen's inner harbour was declared clean enough to swim in only in 2002. For most of the twentieth century it was an industrial channel: coal quays, shipyard cranes, the Burmeister & Wain engine works pumping oil into water the colour of slate. The transformation was deliberate and expensive, and it changed what the canals are for. The waterway itself is older than the industry that fouled it. Christian IV cut Christianshavn's canals in the 1610s on a Dutch model, ringing the new merchant quarter with defensive water and mooring space. Nyhavn followed in 1671, dug by Swedish prisoners of war as a working entrance for cargo vessels sailing directly to the market at Kongens Nytorv. The gabled houses at numbers 20 and 67 — Hans Christian Andersen lived in both — were merchants' warehouses before they were photographs. Slotsholmen's moat, the granite bulk of Christiansborg, the black basalt of the Royal Library's extension: all of it was designed to be read from the water first. That original orientation is why yacht rental copenhagen has become the city's most articulate form of sightseeing. From a boat, the Opera House and the Royal Playhouse face each other across the harbour as their architects intended, a dialogue invisible from any pavement. The Little Mermaid sits at eye level on her Langelinie boulder rather than behind three rows of shoulders. Amalienborg's four rococo palaces open onto Frederiksstaden's axis, which terminates at Frederik's Church and, in the other direction, at the quay. The fleet has changed more than the route. Electric propulsion arrived in the harbour in the 2010s and is now standard on the small hire boats moored at Islands Brygge 10, which means passage under Christianshavn's low bridges happens in near silence — no diesel note, no wake, no smell. Cormorants tolerate it. So do the swimmers at Havnebadet, a few metres off the beam. Copenhagen carries roughly 400 kilometres of cycle track and rather less discussion of the water that shaped its street plan. Yet the city's UNESCO-adjacent heritage sites, its warehouse conversions at Nordatlantens Brygge, and its newest architecture at Refshaleøen all sit on quaysides. A yacht rental copenhagen tour restores the sequence. The buildings return to their proper foreground, and the harbour stops being a gap in the map.