Before I left the U.S., I asked for tips on where I should go in Paris. My friend Marie-France directed me to a park set atop old railroad tracks near the Bastille Opera (which was built at the site of a demolished train station).

"The Opera Bastille, built in 1988 by Carlos Ott, is ... now connected to a very interesting elevated garden pathway called 'Promenade Plantee.' Many Parisians aren't aware of it, but it's a 3-mile-long walkway that follows an old railway and allows you to explore the 12th arrondissement from 10 feet up," she wrote to me.

I did the walk around 7 p.m. Friday evening ... not crowded, but full of spring flowers and the bugs that go with them.