When Montpellier was founded in 985, cities were for survival. Most people went out to work in surrounding fields, and didn’t have time or energy or space for greenery. 
We have watched Montpellier evolve over the years, ridding the narrow streets of its historic center of cars and introducing a profusion of vines that completely change the character of a place that otherwise is stone on stone.
In 2017, Montpellier launched a “vegetation permit” to encourage “microflowering” by geting individuals to plant greenery around them–in small communal gardens, containers, wherever roots could find dirt. The city also is planting 1,000 trees a year.
The result is lovely. I can think of all the practical arguments against such climbing vines–they destroy the mortar joints of walls, they are full of creepy crawlies like spiders, they hold humidity, which also is bad for the walls, they tangle with electric wires. 
And yet, I can’t help but be charmed. The streets become magical passages suitable for fairies, especially with the garlands that were strung.
Some of the garlands were made with bits of lace, very romantic.
Some were colorful, very dramatic.
You can’t just look up, because sometimes the surprises are underfoot. And you might not even be aware you’re walking on a rainbow if you aren’t going up.
Everywhere that the narrow streets open even a little, to a space not worthy of being called a square, there are trees squeezing up between the cream-colored stone buildings, and café tables spreading beneath them.
Behind the façades, too, are hidden gardens. Real gems. 
Others, who have neither garden nor sidewalk, make do with balconies.
I think it’s a brilliant idea. The climate around here is such that these vines stay green year-round. The city says one benefit is they help clean the air.
What’s not to love about that?
Taste of France 