It is not an urban sci-fi fantasy: Someone is building a leafy underground park below Delancey Street on Manhattan's Lower East Side.
The Lowline is a plan to turn an abandoned trolley terminal there into a public green space, using special technology that pipes in sunlight beneath the street's surface.
The real deal probably will not be ready until 2020, but this week, the creators opened the Lowline Lab, a proof of concept and an experiment for seeing the ideas and technology in action. Here are 10 things to note.
1 THE LOWLINE LAB
This collection of wooden terracing, metal canopy and live plants is the Lowline Lab. At just over 1,200 sq ft, it is about 5 per cent the size of the actual Lowline space, but it is big enough that if you stand in the centre, you get a sense of what the full park might feel like.
It will be open through at least March next year, letting the designers see how the structures and plants react to a New York City winter, and might evolve over time.
2 THE CREATOR
Mr James Ramsey is the man responsible for the Lowline. Along with co-founder and executive director Dan Barasch, he started laying plans for an urban underground park in 2008. He is the one who invented the optical systems that transport the sunlight from above ground to the Lowline and made it suitable for growing plants in otherwise dark spaces.
3 ENTERING THE LAB
The Lowline Lab sits at 140 Essex Street, a former market building in New York's Lower East Side.
When you enter the lab, you are greeted by a series of panels explaining the history of the neighbourhood, the goals of the Lowline and the science behind making it work.
Those tubes overhead that look like fluorescent lights? They are actually polycarbonate "plumbing" tubes fitted with mirrors and lenses that bring sunlight from the roof to the interior of the lab. That glow is all from the sun.
4 DIVING IN
Even though the Lowline Lab is a miniature example of the immersive park, the designers want visitors to be able to get a sense of what the finished park will feel like.
You can walk through a cut-out that runs straight through the middle and discover the plants and structure up close.
Because the lab is set in the middle of a larger room, it appears much darker here than it actually is and one of the goals of the lab is figuring out the best ways to distribute light across the landscapes.
5 GROWING EDIBLE PLANTS
All of the plants in the lab are real and some of them are even edible. There are pineapples, mint, thyme and strawberry plants mixed in with the more decorative ground cover. There are more than 60 species of plants in total.
6 THE ANODISED ALUMINIUM CANOPY
The segmented canopy is critical to making things grow underground. The combination of hexagonal and triangular anodised aluminium panels form a flexible canopy that can adapt to the needs of what is growing in the lab. The structure can direct light wherever it is needed and keep the "light plumbing" out of sight, so visitors can enjoy the atmosphere without being fixated on the technology.
7 AN EVOLVING ECOSYSTEM
Mr Ramsey recently found a tree frog that he says must have been hiding in a fern while the ground cover was being planted. So far, it is the only animal calling the lab home, but he hopes more animals and insects will colonise the place. The idea is that the plants and animals create an ever-evolving ecosystem.
8 UTILISING THE SUN
The only artificial light in the lab is around the edges of the minipark.
The completed Lowline will not have any artificial light at all. Light is piped into the plumbing system through mirrored collectors, which focus the sunlight into a concentrated beam that is 30 times brighter than ambient sunlight.
The Lowline will use more than 100 of these collectors. Mr Ramsey's plan is to integrate them seamlessly into the downtown landscape.
9 BRINGING LIGHT UNDERGROUND
While some smaller collectors track the sun directly, larger ones use massive tracking mirrors to push the sunlight into their view.
Both the mirrors and collectors have coatings to filter out infrared light while keeping the ultraviolet parts. This prevents the devices from getting hot - they would be extremely dangerous otherwise - while keeping the wavelengths needed by plants and animals.
The collectors are made by Sun Portal, a South Korean company working with the Lowline.
But you cannot just blast a garden with a concentrated beam of sunlight and expect anything good to come of it. A set of lenses is embedded into the canopy, softening the light, and then a chandelier-like set of reflectors further distributes it across the lab. By using the canopy, lenses and reflectors together, the team can create an array of light conditions across the landscape.
10 THE CANYON
The central corridor is a simulated canyon, made from terraced plywood that contains the gardens. The shape is a replica of part of Antelope Canyon, a famous geological formation in Arizona. The wood gives the garden its shape, while the plants are grown in soil, just as they would be outdoors. Visitors can see how the light shifts as they move across the landscape.