There's a change of pace in Paris on Sundays. Many of the shops, and even some of the restaurants are closed. In the morning the streets are deserted, but by lunchtime and in the afternoon they're filled with people walking, chatting and enjoying themselves. The pace is less frenetic than the busy weekdays.
So, from my viewpoint, what can people do in Paris on Sundays?
They can window-shop along le Viaduc des Arts where the arches beneath the no-longer-used viaduct have been glassed in to provide light-filled shops and ateliers for (very upmarket) craftspeople
If they're fortunate, as we were, they can lunch in a trendy restaurant created under the Viaduc arches (my friend had suckling pig; I had a tarte tatin of confit of chicken with mashed potatoes)
They can stroll along the elevated walkway that's been created on top of the Viaduc
and listen to a group of musicians playing in the metro.
They can ride on the carousel
or skate on the ice rink that's been erected in front of the grand Paris Hotel de Ville (Town Hall)
or just meet up with friends in the park.
They can buy waffles or donuts or crepes from a stall in the square (we easily resisted this - still full from lunch, despite the long walk, and anyway having so many other more wonderful food temptations)
or they can sit in a cafe and watch the world pass by.