Copenhagen Towers Walk — Round Tower, Kastellet and a Canal Bike Ride

Copenhagen’s old town, it turns out, is a city rigged for being seen from above. Stand on the roof of the Round Tower, a 17th-century observatory; walk the earthen ramparts of the star fortress Kastellet; then finish by cycling along the canals — a towers-and-fortress walk that fits into half a day.

The short version — why this route works

1. The Round Tower is the city’s easiest viewpoint at 40 DKK: you climb a spiral ramp, not stairs — a structure like nowhere else. More satisfying than the Little Mermaid, if we are honest
2. Kastellet is free: an active military site whose rampart walkways are nonetheless open to all. In autumn it becomes a foliage hotspot
3. On foot plus a bike, it is half a day: Round Tower → Kastellet → Little Mermaid runs in a straight line. Rent a bike for the finish and you get to feel the world’s greatest cycling city
4. October is the sweet spot: pair the foliage with Halloween at Tivoli Gardens and you get a rich trip well clear of the summer high season

The Round Tower — a spiral ramp to the roof (40 DKK)

Built in 1642 as an observatory for astronomers, the Round Tower (Rundetaarn) has one defining quirk: there are almost no stairs inside. You walk up a cobbled spiral ramp that winds around seven and a half times. It was designed so horse-drawn carts could haul instruments to the top — and in 1716, Russia’s Tsar Peter the Great is recorded to have ridden up on horseback. The slope is gentle, and about 10 minutes brings you to the rooftop deck. Copenhagen has no high-rises, so even a 34.8m tower commands the whole city. Entry is 40 DKK (covered by the Copenhagen Card), and needing no reservation, it has the charm of a place you can simply wander into.

Kastellet — a star fortress in autumn colors (free)

A walk of about 25 minutes northeast from the Round Tower (or two metro stops) brings you to the moated star fortress Kastellet. Built in the 1660s, it is one of the best-preserved star fortresses in Europe — and though still an active military site, entry is free. The rampart walkway tracing the star’s bastions runs about 2km around, and in October it is a tunnel of golden leaves. Red barracks, a windmill, autumn colors mirrored in the moat — nothing flashy, yet this may be the most paintable walk in Copenhagen. Exit past St Alban’s Church and the Gefion Fountain just to the south, and the Little Mermaid is five minutes on foot. Even the Mermaid — famous as a letdown — somehow makes sense when she appears mid-route like this.

Finish on two wheels — riding the world’s great cycling city

In Copenhagen, roughly half of all commutes happen by bicycle — this is one of the world’s great cycling cities. Lanes fully separated from cars and sidewalks, bicycle-only signals, hand signals for turning — riding through a city where the bicycle rules the road is sightseeing in itself. Rental shops and share bikes are everywhere; from the Little Mermaid, cruising the canalside to Nyhavn takes about 20 minutes. Only three rules: keep right in the lane, raise a hand when stopping, and stay off the sidewalks. Local traffic moves fast in the evening rush, so daytime rides are the comfortable choice.

Practical notes for the towers-and-fortress walk

• Model route (half a day) — Round Tower (1 hour) → 25-minute walk → Kastellet loop plus St Alban’s Church (1 hour) → Little Mermaid (15 minutes) → by bike to Nyhavn (30 minutes)
• Prices — Round Tower 40 DKK (Copenhagen Card accepted); Kastellet, the exterior of St Alban’s and the Little Mermaid are free (as of July 2026)
• Best season — October, for the foliage, is our top pick. In summer the long daylight lets you stay out walking until 9 pm
• Watch out — Kastellet is an active military site: obey the no-entry signs. And do not walk in the bike lanes (cyclists will ring their bells at you)
• Combine — spend the evening at Tivoli Gardens. If you want it all in one day, the Copenhagen Card (transport plus admissions) comes out ahead

Where to go from here

• The full trip design → Copenhagen Travel Guide
• An amusement park for the evening → Tivoli Gardens Guide
• Choose your next trip by scenery → Scenic Travel Destinations