Self-guided vs operator-led
Self-guided architecture walks (with city's architecture-society maps) cost zero and let you set pace. Operator-led tours (€20–40 typically) include interior access to private buildings closed to general public. Both work; operator-led better for first visit.
Vienna
Vienna Otto Wagner walking tour route — Postsparkasse, Karlsplatz Stadtbahn, Majolikahaus, Wagner-built apartment buildings (6th and 7th districts). Plus Adolf Loos's Looshaus and Café Museum. Vienna Tourism Board provides downloadable PDF route.
Barcelona
Barcelona Modernisme route — Sagrada Família, Park Güell, Casa Batlló, Casa Milà, Hospital de Sant Pau, Palau de la Música. Eixample grid + the Passatges full Modernisme density. Architects: Gaudí, Domènech, Puig i Cadafalch.
Berlin
Berlin postwar architecture walks — Hansaviertel housing estate (Le Corbusier, Aalto, Niemeyer), Karl-Marx-Allee (East Berlin Stalinist boulevard), Bauhaus-Archiv. Plus contemporary architecture walks (Sony Center, Reichstag dome, Holocaust Memorial).
Glasgow
Glasgow Charles Rennie Mackintosh trail — Glasgow School of Art (rebuilt), Hill House (Helensburgh, day-trip), Mackintosh House at Hunterian, Willow Tea Rooms. Mackintosh Society organizes tours.
Brussels
Brussels Art Nouveau walks — Horta House, Solvay House, Hotel Tassel, Hotel van Eetvelde. Saint-Gilles and Ixelles districts. The Horta Foundation organizes guided interior visits.
Rotterdam
Rotterdam contemporary architecture walking tour — Cube Houses, Markthal, Erasmus Bridge, Centraal Station, De Rotterdam (OMA tower). Rotterdam Architectural Walks operator.
Strategy
Architecture walks 2.5–3.5 hours typical. Wear walking shoes. Bring binoculars for upper-floor details. Modernist guide + Art Deco guide + Baroque guide for detailed style backgrounders.