Here's an update since my 2005 posting, now identifying the sites visited. I'm up to 51 or 52 (depending on whether "drive-bys" count

) from 40. It's progress, but not as much as I would like. Will just have to keep working on it (will be able to add a couple of new sites after our Italian cruise this October).
Austria:
Historic Centre of the City of Salzburg
Palace and Gardens of Schönbrunn
Hallstatt-Dachstein Salzkammergut Cultural Landscape
Historic Centre of Vienna
Belgium:
Flemish Béguinages
Grand-Place, Brussels
Major Town Houses of the Architect Victor Horta (Brussels)
Historic Centre of Brugge
Plantin-Moretus House-Workshops-Museum complex (Antwerp)
Canada:
Kluane/Wrangell-St. Elias/Glacier Bay/Tatshenshini-Alsek
Historic District of Québec
Rideau Canal
Czech Republic:
Historic Centre of Prague
Historic Centre of Český Krumlov
Denmark:
Kronborg Castle
France:
Palace and Park of Versailles
Strasbourg - Grande île
Paris, Banks of the Seine
Germany:
Pilgrimage Church of Wies [drove by it - does that count?]
Palaces and Parks of Potsdam and Berlin
Town of Bamberg
Cologne Cathedral
Museumsinsel (Museum Island), Berlin
Monastic Island of Reichenau
Upper Middle Rhine Valley
Old town of Regensburg with Stadtamhof
Hungary:
Budapest
Israel :
Masada
Old City of Acre
White City of Tel-Aviv -- the Modern Movement
Bahá’i Holy Places in Haifa and the Western Galilee
Italy:
Venice and its Lagoon
City of Verona
Jerusalem:
Old City of Jerusalem and its Walls
Mexico:
Pre-Hispanic City of Chichen-Itza
Netherlands:
Historic Area of Willemstad, Inner City and Harbour, Netherlands Antilles
Saint Lucia:
Pitons Management Area
Switzerland:
Old City of Berne
Convent of St Gall
Jungfrau-Aletsch-Bietschhorn
United Kingdom of Great Britain and Northern Ireland:
Westminster Palace, Westminster Abbey and Saint Margaret's Church
Tower of London
Old and New Towns of Edinburgh
Maritime Greenwich
United States of America:
Kluane/Wrangell-St. Elias/Glacier Bay/Tatshenshini-Alsek
Independence Hall
Redwood National Park
Olympic National Park
La Fortaleza and San Juan Historic Site in Puerto Rico
Yosemite National Park
Hawaii Volcanoes National Park
Monticello and the University of Virginia in Charlottesville