Amsterdam is shutting a third of its brothels.
One of the main brothel owners is set to sell his empire to a property firm.
A housing company is to buy 18 premises, currently featuring 51 windows, for about 25 million euros ($35 million), Amsterdam city council said.
The mayor says although prostitution is legal in the Netherlands there's too much of the sex trade in the capital and said the windows are a magnet for crime and money laundering.
Mayor Cohen said: "What we do want is to get rid of the underlying criminality," he said.
Dutch sex workers' union De Rode Draad said: "We believe that less windows means more exploitation of women," spokeswoman Metje Blaak told the AFP news agency.
"If the windows close down, women who are being exploited will be hidden somewhere else where union representatives and health workers can't make contact with them," she said.