It’s been a long time since Clark Kent could pop into a phone booth and emerge as Superman. There simply aren’t many walk-in booths left anymore. In New York, they’re being replaced with Wi-Fi hot spots as part of a program called LinkNYC, touted as the largest, fastest, free municipal Wi-Fi network in the world. The city began installing the sleek kiosks in December. Five hundred are due to be in place by August, with the goal of at least 7,500 across all five boroughs by 2024. Besides Wi-Fi, each station will provide two USB charging ports, a built-in tablet for Internet access, and a 911 call button. It’s all free, paid for with advertising revenue from each kiosk’s two 55-inch screens. But should you grow nostalgic for the classic phone booths, you can find four along West End Avenue on the Upper West Side. They’ve been saved -- although the booths themselves have been refurbished, the phones have been updated and the calls are now free.