ISTANBUL — On a cold and wet morning here, half a dozen men were lined up at the metal gate that blocks off an alley called Giraffe Lane in the Beyoglu district, their collars turned up against the rain and their hands shoved into their pockets.

Having shown their identification to the police officers guarding the gate, they handed over mobile phones, key rings and cigarette lighters to a custodian, shuffled through a metal detector, and sauntered off to take their pick of the brothels that line the lane.

Every day, from 10 a.m. until 10 p.m., men make their way in a steady trickle down the steep back alleys below the Galata Tower to disappear behind the gate guarding Giraffe Lane, a cul-de-sac that is Turkey’s oldest legal and licensed red light district.

Founded over a century ago in Ottoman times, the brothel district still serves over 5,000 men a day, even though its heyday is clearly over, with most of its decrepit apartment buildings now empty.