The three that do it for me are St. Marks for the reasons mentioned, Bruges as the best square to hang out until late at an outside table, and Prague's main square in old town for its fantastic array of architecture of different periods.

Another vote for Place Stanislas in Nancy (and also Dijon place de la libération of course :-d )

I have visited some of the beautiful squares mentioned here and my vote is for Red Square.

It is beautiful (although large), especially at night with the red stars on the top of the Kremlin or in the winter with snow on the ground. And you just cannot beat the awe of standing in Red Square!

I am fond of a few piazzas in Rome but nothing beats St Mark's in Venice.

In addition to the above, I would say the square in Telc, Czech Republic.

There is a beautiful sq. in Barcelona. I wish I knew the name of it. We stopped there for tapas one evening about 7:00. Maybe someone can help. Its more then halfway down the Las Ramblas, definitely past the food market. You make a Left turn, (we were strolling) and it is
in the Bari Gotic, about 1 or two blocks off of Las Ramblas. I keep thinking there was a government building or station on the sq. at 1 end. Wow, it was stunning. Anyone know what I'm thinking of, by my directions?

My vote is Place de Voges in Paris, lots of relaxing locals.

I love the Piazza Bra in Verona. Sipping a Martini Bianco while gazing at the Roman ampitheater is my idea of heaven!

One of my alltime favorites is the Piazza 9 Aprile in Taormina, Sicily.

http://www.pbase.com/elsinger/image/62304830

Here's another view:
http://www.pbase.com/elsinger/image/62304831

I'll have to say Trafalgar Square in London is a favorite. With Lord Nelson & his Lions, the fountain, the National Gallery and St. Martin's in the Fields, and a peekaboo view of Big Ben...That was my first "pinch me, I'm in Europe" moment.

The crazy soccer fans with the traffic cones on their heads, wearing the British Flag and singing God Save The Queen added to the fun of being there too.

Jules

For me its the market square in Brugge. Although not far behind was the square in Delft for i was standing there all by myself - it beats the square in Haarlam hands down in my opinion.

The most bautiful square I've seen in Europe is the main square at Viana do Castelo, Praça da República. http://www.galenfrysinger.com/viana_do_castelo.htm

Certainly not the most beautiful, but the most interesting was the square (circle?) in Siena during the Palio...absolutely incredible experience!!! I have never seen so many people backed onto balconies in my life and the energy of the crowd is spectacular!!

Interesting thread. My favorite squares tend to be places I have a personal connection to and include...

1. Place de la Comedie, Montpellier, France (I studied there in college)
http://en.wikipedia.org/wiki/Montpellier
2. Schlossplatz, Stuttgart, Germany (my current "hometown" square) http://www.vvs.de/download/freizeitp...hlossplatz.jpg
3. Piazza della Rotunda, Rome (just spent Christmas there!)

Place des Vosges in the marais in Paris. Any season it is my favorite.

St. Mark's is gorgeous and romantic
Pantheon is a favorite square of mine in Rome.
Place de Vosges is not overwhelmingly beautiful to me but is lovely place to hang out.
I think that the Old Town Square in Prague is really lovely - beautiful buildings.

Old Town Square is quite striking. I can stare at the Tyn tower for hours & not get bored. I would have to second St Peter's square at night, though. It brought chills down my spine when I walked through it in the dark, with only a handful of others also staring in awe.

Back to Prague, the castle square (Hradcanske Namesti) and the square near the Loreto (Loretanske Nam) are quite beautiful, especially at night, with the street lamps twinkling. Magic every time...

Though I also don't remember the name of the mentioned square in Barcelona off Las Ramblas, it is gorgeous!

Also, main square in Krakow and Old Square in Prague are winners for me. I'm a sucker for the old eastern european architecture

Piazza San Marco in Venezia. Even with the pigeons. Well, so long as it is not under water due to aqua alta.