Schönbrunn Palace — Grand Tour of the Habsburg Summer Residence
Walk the 1,441-room imperial summer palace of the Habsburgs through the Grand Tour (40 audioguide rooms) — including the Hall of Mirrors where 6-year-old Mozart performed — then climb the Baroque gardens to the hilltop Gloriette for the postcard view back over the palace. This is Vienna's single most famous sight, a UNESCO World Heritage site, and the one 'imperial Vienna' moment a first-timer regrets skipping. Book a timed slot in advance on the official Imperial Tickets shop — it sells out daily.