What do you consider to be the most famous - well-known worldwide landmark structures in Europe?

I'll start - ranked in order:

1- Eiffel Tower, Paris
2 - Leaning Tower, Pisa
3- Parthenon/Acropolis, Athens
4- Colosseum, Rome
5 - Stonehenge, England
6- St Peter's, Vatican City
7- Big Ben; Houses of Parliament, London
8- Buckingham Palace, London
9 - Neuschwanstein Castle, Fussen, Germany
10- Mont-Saint-Michel, France

WHAT DO YOU CONSIDER THE TOP TEN ICONIC OR LANDMARK SITES IN EUROPE - ones that most folks would rank - i.e. the most famous structures in Europe and not necessarily yours (or mine in the above ranking) but what most folks would rank, even if they had not been to Europe.

You've covered it pretty well, Pal. For 10b you could add the Alhambra in Granada, Spain; for 10c, St. Sophia in Istanbul; for 10d, Dutch windmills.

and I now am thinking perhaps Brandenberg Gate, Berlin?

Piazza San Marco. No place like it.

I'd replace #9 with Sagrada La Familia or the Alhambra.

My top 10 would include
Eiffel tower with
Versailles and
Notre Dame replacing #5 & #9.

what Happy said

Neuschwanstein was one of my all timebiggest travel disappointments. Should have skipped it.

I would nominate Pont du Gard.

1. Colosseum, Rome
2. St. Peter Basilica, The Vatican
3. St. Mark Basilica & Square, Venice
4. Eiffel Tower, Paris
5. Leaning Tower, Pisa
6. Notre Dame, Paris
7. Roman Forum, Rome
8. The Arch, Paris
9. Big Ben Tower clock, London
10. La Sagrada Familia

If we are talking just top 10, then yeah the icons are pretty much in Italy and France, other landmarks rank below them

1. The Vatican, Rome
2. Colosseum, Rome
3. Piazza di San Marco, Venice
4. Parthenon, Athens
5. Eiffel Tower, Paris
6. Fontana di Trevi, Rome
7. Pantheon, Rome
8. Notre Dame, Paris
9. Milan Duomo, Milan
10. Mont St. Michel

In no particular order( and not necessarily 10):
Eiffel Tower;Collosseum;Sagrada Familia;Hagia Sofia and Blue Mosque;Panteon(Rome); Notre Dame;Mont Saint Michel;Piazza San Marco;Versailles;Saint Peter Kirche(Vienna).

Which of these churches would you recognise if they were in a line up with other churches of the same era

Uk houses of parliament
Big Ben clock tower
Gerkin
Eiffel T
La sagrada familia
Buckingham Palace, London
Neuschwanstein Castle
San Marco
Hagia Sofia
Stonehenge
Leaning tower

These are the only ones in the list above that I would even recognise, I've been to most of the others but I doubt if I could tell most of the fountains, churches and flim flam from others. Interestingly only the Gherkin stands out as a modern piece.

Monts St Micheal I'd confuse with St Michael's mount,
Colliseum with the one in Pula, Trevi with half a dozen fountains around Europe, St Peter's bits and pieces with half a dozen old churches,

You could add Buck Palace and "No 10"

I wonder if the Mannequin Pis in Brussels qualifies as a structure?

Definitely must include La Sagrada Familia, instead of Neuschwanstein (sp?)

Aqueducts and colossei throughout the former Roman territories, e.g., Pont du Gard (ala DebitNM), Arles, etc.

All of Venice
Amsterdam Canals
Gaudi' edifices in Barcelona
La Mezquita de Cordoba
Chateaux of the Loire Valley
Caves of SW France
Alhambra and Generalife
The Louvre and The Prado
Champs Elysee

Most famous? well-known? as opposed to most eye-pleasing?

I'm forced to say Disneyland-Paris.