Can I leave the airport on a layover in Copenhagen?

Copenhagen Kastrup (CPH) is 8 km south of the city center. The Metro M2 departs Terminal 3's basement level every 4-6 minutes and reaches Kongens Nytorv in 14 minutes for 38 DKK, about $6. If you arrive from outside the Schengen zone, passport control tends to take 10-15 minutes. Flights within Schengen skip immigration entirely. Allow 90 minutes before departure for return security and the gate walk. Do that arithmetic on your own connection time and the number of usable city hours becomes clear. If it does not add up, stay airside. Terminal 2's Joe & The Juice has decent flat whites, and the airport is compact enough that a shorter wait passes faster than you would expect.

From Kongens Nytorv station, Nyhavn is a 3-minute walk north. The canal's painted townhouses date to the 1680s, and they look better under overcast skies than in any postcard. Half the people leaning on the iron railing at midday are traveling alone, so you will not feel conspicuous. The herring plate at Cap Horn on the north side runs about 155 DKK, served on heavy ceramic with a cold Tuborg. Walk 10 minutes west along Gothersgade and you reach Rosenborg Castle, built in 1606 for Christian IV. The King's Garden around it smells like cut grass and linden in late summer, and the benches fill with locals on their lunch breaks. Entry is 130 DKK. The crown jewels sit in the basement vault, and 45 minutes covers the whole building without rushing.

Solo safety in Copenhagen scores 7.8/10 (see the TTDI Solo-Safety Index), and the number tracks with reality on the ground. I would walk Indre By, Vesterbro, and Nørrebro at midnight without a second thought. Christianshavn is fine too, though the Pusher Street section of Freetown Christiania has its own rules, and photography there will get your phone knocked from your hand. For a layover, stick to the Metro M2 corridor and you will not encounter anything concerning. The M2 runs 24 hours on Friday and Saturday nights. Weeknight service ends around midnight, so budget for a taxi back to CPH after that, around 80-120 DKK from Vesterbro. Torvehallerne, the glass-roofed market hall two minutes from Nørreport station, is the best solo-dining stop during a layover. No reservations, no party-size minimums. Hallernes Smørrebrød sells open-faced rye sandwiches from 65 DKK. Sit on the metal stools outside with a coffee and listen to commuter chatter bouncing off the glass canopy above you.

Tivoli Gardens, open since 1843, sits across the street from København H station, 13 minutes from CPH by regional train. Entry runs around 160 DKK, rides cost extra, but the grounds alone fill 60-90 minutes without them. The air inside smells like spun sugar and warm wood from the older carousel. Late August evenings in Copenhagen settle around 16°C, so bring a layer for an after-dark visit. Skip the Little Mermaid, a 1913 bronze near Langelinie, unless you feel strongly about it. It sits 30 minutes north of the nearest Metro stop and draws tour-bus crowds that make the approach slow. That time is better spent at Gasoline Grill on Landgreven 10, where a 95 DKK burger from a converted gas station is the best meal under 100 DKK in the inner city.