What's the must-see thing in Copenhagen?

Skip The Little Mermaid. Half the visitors I know who went there first spent twenty minutes finding it, took one photo of a surprisingly small bronze figure on a rock, and felt deflated. Rundetårn earns its spot because nothing else in Copenhagen does what it does in so little time. The ramp is wide enough that Peter the Great reportedly rode a horse up it in 1716 — your feet hit smooth cobblestones that have been worn glossy over four centuries, and the incline is gentle enough that you barely notice you're climbing. At the top, the open-air platform puts every landmark in context: Christiansborg's green copper tower to the south, the Marble Church dome to the northeast, the harbor cranes beyond. Ten minutes up, ten minutes to get your bearings, done. Forty DKK — about six dollars.

Rosenborg Castle sits at the far end of Kongens Have, the oldest royal garden in Copenhagen, and the approach through those lime tree alleys on a June morning — cool shade, the sound of gravel underfoot, joggers passing the 400-year-old hedgerows — is half the visit. The castle itself is a Dutch Renaissance brick building from 1606 that still feels like someone's extremely wealthy summer house rather than a museum. The crown jewels are in the basement: Christian IV's diamond-and-pearl crown under thick glass, surprisingly close, no velvet ropes keeping you three meters back. Budget ninety minutes. Tickets are 130 DKK (roughly twenty dollars), and the Copenhagen Card covers it. The gardens are free and open from 7am — worth going early if you want the place almost to yourself.

Nyhavn is the postcard and everyone knows it. The colored townhouses along the canal — ochre, deep red, dusty blue — do look exactly like the photos, which is rare. Hans Christian Andersen lived at number 67, then 18, then 20 over different decades, and the buildings carry small plaques if you look. Here's the trade-off: the sunny side (the north bank) is where every tourist sits with overpriced beer, and it smells like frying oil from the restaurants packed shoulder-to-shoulder. Walk to the shady south side instead. The view is better — you're looking AT the colored facades rather than sitting in front of them — and the bars charge about 20 DKK less per pint. After 8pm on summer evenings the light turns golden across those facades and the crowds thin. That's the version of Nyhavn worth seeing.

A note on The Little Mermaid, since every guidebook still lists it near the top: the statue is 1.25 metres tall, sits on a rock at Langelinie about two kilometres north of the center, and there is nothing else at that end of the harbor worth the detour unless you're also visiting the Kastellet star fortress nearby. If you do go, the walk along the waterfront from Nyhavn takes about twenty-five minutes through Amaliehaven past the Opera House — the route is honestly better than the destination. But if your time in Copenhagen is short, those twenty-five minutes are better spent at Rosenborg or inside Designmuseum Denmark on Bredgade, which has the strongest collection of Danish chair design anywhere and costs 130 DKK.