My top 10 buildings

1. Battersea Power Station, London, Great Britain

   (at least in its original state; what the current redevelopment will bring remains to be seen)

 

2. The Eiffel Tower, Paris, France

 

3. The Chrysler Building, New York, USA

 

4. Hagia Sophia, Istanbul, Turkey

 

5. The TV Tower on Alexanderplatz in Berlin, Germany

 

6. The Firth of Forth railway bridge, near Edinburgh, Scotland, Great Britain

 

7. The State Historical Museum at the northern end of Red Square, Moscow, Russia

 

8. Buzludzha monument, Bulgaria

 

9. Westminster Cathedral (not Abbey!), London, Great Britain

 

10. Yeni Camii mosque, Istanbul, Turkey

… plus any of the grand gothic cathedrals (from Notre Dame in Paris or the Stephansdom in Vienna to Cologne Cathedral, Chartres Cathedral, Wells Cathedral, Canterbury Cathedral … and any on a similar scale. I just couldn't single any one of them out …

 
… and then of course there are those buildings that would easily take the place of some of the buildings I've listed above, but which I haven't yet seen in the flesh, such as the pyramids of Egypt, or Sydney Opera House, Australia.