In the heart of ancient Athens, on narrow streets and around archaeological sites, visitor groups appear to be everywhere, snaking their way behind tour guides. Previously, officials would have welcomed such scenes. But for Haris Doukas, the socialist mayor who is determined to reclaim the capital’s congested city centre for its citizens, the start of tourist season leaves the city at risk of “over-saturation.” Entire neighbourhoods, he believes, are in danger of losing their authenticity because of uncontrolled tourist development. “Athens cannot operate as if it were a giant hotel,” he said in an interview. “Restrictions and rules are needed. Cities must also have a say in the way they develop.” Last year, more than 8 million people visited Athens, a record for a city that not long ago was regarded as a pit stop to the Greek isles.…