How would the circular economy actually work in practice? To find out, all we have to do is look within an abandoned indoor waterpark that sits on the banks of the river Maas in Rotterdam.

Yes, a derelict swimming pool may seem like a strange place to see the circular economy in action, but the old waterpark, formally known as Tropicana, has been taken over by 30 businesses that all share resources and reuse the waste in a trial “circular economy”. They call it BlueCity. Tropicana had fallen into disuse in 2012, but to entrepreneur Siemen Cox, the structure of the building looked like a giant greenhouse—which was perfect for Cox, who was looking for a site to grow mushrooms using coffee grounds.

Cox was able to convince investors and city officials that the old Tropicana could become an ecosystem of circular entrepreneurs, and well, the rest is history. Beneath the pool are craft brewers Vet & Lazy who are developing a pioneering chemical-free rainwater purification system, and the circular caterer Arabella van Aartrijk, who bakes cookies from Vet & Lazy’s spent grain and rescues “ugly” food. In other parts of BlueCity, old mangoes are mashed into leather and used plastic is 3D-printed into new products.

Want to see for yourself what the circular economy could like? If so, look no further.