The Lowline, the world’s first underground park, just cleared a huge hurdle

Good news for fans of subterranean flora: New York City officials just gave the green thumbs-up to build the Lowline, the world’s first underground park in an abandoned trolley terminal in Manhattan. The project, which is meant to be the converse of the tremendously popular High Line park — which was built on a disused elevated rail spur — aims to use its own unique sunlight-capturing technology to grow its own mini-forest below street level and next to an active subway line.

But getting the approval from city regulators is just the first of many tasks the Lowline’s creators will need to overcome. Over the next year, they’ll have to raise $10 million, convene a series of design and community outreach meetings, and submit detailed...