Skating, George Square

What do the following have in common -

Rockefeller Centre, New York;
Red Square, Moscow
George Square, Glasgow;
Somerset House, London,
Frog Pond, Boston
Millennium Park, Chicago
Eiffel Tower, Paris
The Zocalo, Mexico City
Central Park, New York City

Yes, they are rated the top venues for outdoor skating at Christmas. (O.K. then, I slipped in the one about George Square when no one was looking).
George Square may not be as glamorous as the other venues in the list but the people on it today were sure enjoying it.

As a postscript I have to say its not an easy photograph to get as they aren't at all keen on photography at this location. I have deliberately processed the picture in such a way that none of the participants can be identified. Hopefully everyone is happy.