What's the must-see thing in Salzburg?

Hohensalzburg Fortress is the right answer because it does something no museum or concert hall in Salzburg can. It gives you the whole city at once. Archbishop Gebhard built the first structure on Festungsberg during the Investiture Controversy, and nearly a millennium of expansion turned it into the largest fully preserved fortress in central Europe. The thing you feel walking its stone corridors in July is the temperature drop. Outside might be 22°C with the overcast humidity Salzburg tends toward in summer. Inside the Burgmuseum rooms, the air cools to maybe 14°C and smells like cold limestone and iron. From the Reckturm watchtower, you look north across the Salzach River into the Altstadt's grey-green copper domes, with the Untersberg massif filling the southern horizon. On a clear morning you can see the church spires of Berchtesgaden across the German border, about 20 kilometres south. The Festungsbahn funicular from Festungsgasse carries you up in about a minute. Walking takes 15 to 20 minutes on a steep cobbled path that gets slippery after rain.

Go before 10am. The fortress opens at 9:00 from April through September, 9:30 in winter. By 11am, the courtyards fill with tour groups off the Munich day-trip buses and the narrow passages become shoulder-to-shoulder. An early visit gives you 60 to 90 quiet minutes before the crowd wave arrives. The combined funicular-plus-admission ticket runs around €13.80 for adults. Mind you, the walk-only admission is cheaper at roughly €6.60, but the path is steep and exposed. If you have bad knees or it rained overnight, take the funicular up and walk down. The medieval Princes' Chambers on the upper floor still have their original Gothic wood panelling and a ceramic tile stove from the early 1500s. Most visitors skip these rooms for the viewpoints, but the carved woodwork has a dark, oily polish that centuries of hands have worn smooth. That texture is worth the detour.

Salzburg Cathedral sits at the foot of Festungsberg on Domplatz, so you pass it on the way down. The current Baroque structure dates to 1628, though a church has stood on the site since 701. The baptismal font where Mozart was christened on 28 January 1756 is in the left aisle, marked but easy to miss if you don't know to look. Entry is free. A donation of €5 is suggested but not enforced. The interior is cool grey marble and the sound of your footsteps bounces off the 71-metre nave ceiling in a way that makes you lower your voice without thinking about it. The birthplace museum on Getreidegasse, about 4 minutes' walk west, costs €12 for adults. The rooms are small and dim, with low ceilings that amplify the shuffle of every tour group ahead of you. Letters and sheet music line the walls behind glass. Budget 40 minutes. The shopping street outside is narrow, lined with wrought-iron guild signs, and loud with foot traffic by midday.

A lot of first-time visitors try to fit Mirabell Palace, Hellbrunn Palace, and the Sound of Music bus tour into the same day. That is too much. Mirabell Gardens on Mirabellplatz are free and take 20 minutes. The gardens face the fortress across the Salzach, which is the postcard angle you have probably seen already. Hellbrunn is 6 kilometres south and needs a separate half-day. The Sound of Music tours run about 4 hours and cost €50 to €55 per person. They are fine if that is your primary reason for visiting, but they eat the whole afternoon. If you have one day, do the fortress in the morning, the cathedral and birthplace before lunch, and the Mirabell Gardens in late afternoon when the light comes in low from the west and the Festungsberg shadow cools the flower beds. On your way back through Getreidegasse, grab a Bosna from Balkan Grill. The spiced sausage with onions and curry powder in a white roll costs about €4, and the stand has been in the same narrow passage since 1950.