Thousands of years ago, trash was used to insulate homes in neolithic Orkney. In the 1830s, in New York City, Thirteenth Avenue was built atop landfill. In 2005, Singapore opened up an island landfill for nature walks. Trash, in other words, can do more than just stink—it can provide infrastructure that actually benefits cities.

Now, in the Netherlands, FastCoExist reports, one current project aims to trap floating plastic waste before it reaches the North Sea and turn into floating plastic parks.

Plastic flotsam would become huge floating hexagonal building blocks, which would be used to construct the parks. The parks themselves would be planted with grasses and trees and would provide an environment for water-based plants, fish and mussels below. Some of the blocks might even be used to line Rotterdam’s more industrial waterfront.

"Industrialization has damaged the ecosystem in and around the water," project leader Ramon Knoster told Co.Exist, "With the floating parks we will reintroduce a surface for nature."

Baltimore is using a similar system to keep floating trash out of the inner harbor. It hopes to have the harbor clean enough for swimming by 2020, but doesn’t have any plans to build floating islands…yet.

The project in the Netherlands is expected to start collecting plastic in September and build prototype islands next year.