Budapest is two cities that were joined in 1873 and still behave differently. Buda is hills, quiet streets and the castle; Pest is flat, gridded, and where everyone actually lives and eats. Two days splits neatly along that line, and the order matters more than you would think.
Do Buda first. It involves climbing, and climbing is better on a fresh morning than a tired afternoon.
Day one: Buda
Early. Go up Castle Hill before nine. Bus 16 from Deák Ferenc tér takes you all the way up; the funicular is charming and will cost you twenty minutes in a queue. At that hour the Fisherman’s Bastion is empty and free — the ticket booths for the upper terraces are not yet open — and the view east over the river to the Parliament is the one you came for.
Mid-morning. Matthias Church opens next door. Then walk away from the crowd: one street west to Úri utca, where the medieval doorways with their Gothic niches are, and out onto the Tóth Árpád promenade along the western wall. This is the Castle District that most visitors miss entirely, and it takes twenty minutes.
Late morning. Either Buda Castle — the Budapest History Museum rather than the National Gallery, if you want the city rather than its paintings — or the Hospital in the Rock, which is an hour, underground, and needs booking. Not both.
Lunch. Come down off the hill to eat. The restaurants on top are poor value almost without exception.
Afternoon. Walk the Chain Bridge across to Pest and back, or take tram 19 along the Buda embankment to Szent Gellért tér and climb Gellért Hill for the wider view. The climb is twenty-five minutes and the reward is every bridge at once.
Evening. The Gellért Baths are at the foot of the hill and open into the evening. An hour in 38-degree water after a day of walking is the correct decision.
Day two: Pest
Early. The Parliament tour, booked days in advance, in the first slot available. Afterwards walk five minutes south along the embankment to the Shoes on the Danube Bank.
Mid-morning. St Stephen’s Basilica and its dome panorama — lift up, stairs down. From there it is fifteen minutes on foot to the Dohány Street Synagogue, which deserves ninety minutes with the guided tour and the memorial garden.
Lunch. In the Jewish Quarter, which is where the city’s best casual eating is.
Afternoon. Take the M1 — the little yellow line of 1896, itself worth the fare — out to Heroes’ Square and walk into Városliget behind it for Vajdahunyad Castle and the lake.
Late afternoon. The Széchenyi Baths are at the edge of the park. Three hours is not too many. In winter, the outdoor pools in the steam are the single best thing in the city.
Evening. Back into District VII for dinner and, if you want it, the ruin bars. Go early if you want to look at Szimpla rather than queue for it.
What to book before you arrive
Only two things really need it: the Parliament tour, which sells out days ahead in summer and runs in timed language slots, and the Hospital in the Rock. Bath tickets can be bought online to skip the queue but rarely sell out. Everything else you can decide on the day.
If you have a third day
Szentendre is forty minutes on the HÉV suburban railway and is the easy choice — a Serbian Orthodox town of ochre houses on the river. If you would rather stay in the city, Memento Park and the House of Terror make a coherent and fairly brutal day about the twentieth century, and you will understand Budapest considerably better afterwards.
A note on pace
The centre is walkable but larger than it looks on a map, and the two banks are separated by a river you have to cross at a bridge. Trams 4 and 6 run constantly and the metro is quick; buy a 24- or 72-hour travelcard on arrival rather than counting single tickets. Ticket inspectors are real and unsympathetic.
Two things people get wrong
The first is treating the Danube as a street you can cross anywhere. It is three hundred metres wide and the bridges are a long way apart; a route that looks direct on a phone map can add twenty-five minutes because the crossing is not where you assumed. Check which bridge you are using before you set off, not after.
The second is underestimating Castle Hill. It looks like a short walk from the river on a map and it is a hundred and seventy metres straight up. In July, in the afternoon, with children, it is a genuinely bad idea. Take bus 16, or go early.
If it rains
Budapest handles rain badly on the streets and very well indoors. The baths are better in bad weather, not worse — the outdoor pools at Széchenyi in the rain are one of the pleasures of the city. Otherwise the Museum of Fine Arts, the National Museum and the Great Market Hall will absorb most of a wet day between them, and the M1 means you can cross the centre without getting wet for more than two minutes at either end.