The long-weekend European trip — Thursday-Sunday, Friday-Monday, four nights at most — has a different math than a one-week trip. The cost of a slow airport-to-city transit, a boring central neighborhood, or a city you can't dent in 72 hours is much higher when 72 hours is all you have.
The cities that actually work for this format share three properties: the airport is fast to the center, the city's "best of" fits in three full days, and there's enough evening density that you don't waste your one Saturday night.
Tier 1 — the cities that were almost designed for this
Lisbon. The airport metro takes 25 minutes to the center. The city is small enough that 3 days is generous; 4 days lets you do Sintra without rushing. Stay in Baixa-Chiado if you want flat walking, Príncipe Real if you want the design-shop scene.
Porto. Smaller than Lisbon, even more concentrated. A single day in Cedofeita covers the food scene; a half-day handles the port-tasting trip. The wine valleys are 90 minutes by train if you want a fourth day.
Budapest. The transit from BUD airport is the slow part (40-60 min), but once you're in District V the city unfolds quickly. Budapest is denser per square kilometer than most western European capitals.
Copenhagen. 15-min metro from the airport. The center is bike-able end-to-end in 30 minutes. Vesterbro for food-focused trips; Indre By for first-timers.
Krakow. 20-min train from the airport, the entire Kazimierz + Stare Miasto circuit takes two days, the third is for Auschwitz or Wieliczka.
Tier 2 — work great if you stay in the right neighborhood
Berlin. Big enough to overwhelm a long weekend if you try to do everything. Pick a corner of the city — Kreuzberg for food and nightlife, Mitte for sights — and stay in it.
Vienna. The airport train (CAT) is fast but expensive. Stay in Neubau rather than District 1 unless you're prepared to pay a premium for the doorstep-Stephansdom thing.
Prague. The catch is the airport — there's no train, just a bus or taxi. Once in town, Vinohrady beats Old Town for almost every long-weekend traveler.
Amsterdam. Fast train from Schiphol (15 min). The city is small but the canal-belt walks fill 3-4 days easily. Jordaan for first-timers; De Pijp for food-focused.
Tier 3 — possible but tight
Rome. Three days is too short for first-time Rome and too long for repeat Rome at this rhythm. If you must, stay in Centro Storico and accept the price premium.
Paris. The metro from CDG is doable but exhausting on a Friday night. Three days only works for second-time Paris travelers who already know the city.
Barcelona. The airport is fast but the city is genuinely big. Stay in Eixample and resist the urge to do everything.
The cities that DON'T work as long weekends
London. The airport-to-center time alone eats half a day, prices punish short stays, and the museum list demands a full week.
Istanbul. The airport is far, the city is enormous, and split-continent geography means you'll lose hours on every plan.
Madrid. Too big for three days, too sprawling for the long-weekend rhythm. Save Madrid for a five-day minimum.
The bottom line
If you're picking purely on long-weekend friendliness: Lisbon, Porto, Copenhagen, Krakow. Each one rewards the format. Each one leaves you wanting more, which is the right outcome.