ISTANBUL — The Italians have a saying for it: “Fuma come un turco,” meaning, “He smokes like a Turk.”

There are actually plenty of people who smoke more than the Turks, but there are times when a visitor here may find that hard to believe.

The famous Istiklal Avenue, one of the world’s most appealing pedestrian spaces with its cobbled pavement and little red trams clacking down the middle, bells dinging, can be covered over on a crowded weekend night by an inescapably dense, mile-long cloud of secondhand smoke, hovering between the elegant, tall buildings on either side.

Along dusky alleyways in Kadikoy, the trendiest part of Istanbul, on the once less fashionable Asian side of the Bosporus, cafes typically have a few tables inside and many more outside — where smoking is allowed. On even the coldest days, the outside tables are crowded, smokers kept warm by overhead heaters and lap blankets provided at each chair.