As cities around the world look to integrate more greenery into their urban landscapes, rooftops could offer a solution to the problem of land scarcity in growing urban areas. However, a new book from architecture firm MVRDV explores more useful ways to transform roofs in order to improve the resilience and liveability of our cities. The book, called Rooftop Catalogue, takes the Dutch city of Rotterdam as an example of best practices.

The Dutch city is well known for its innovative way of finding uses for often-ignored urban spaces. For instance, one of the hospitals in the city boasts a rooftop where patients can go to visit a small orchard filled with fruit trees. Next to it, an art museum has a rooftop forest planted with birch trees, while a nearby 4,000-foot-long building is topped with a park that has vegetable gardens, picnickers, and grazing sheep.

“Rooftop use could make a huge contribution to the densification of the city—and it could also prevent us from building more on the outskirts of our cities,” Winy Maas, co-founder of MVRDV. The team calculated that if ten percent of Rotterdam’s roofs were used for housing, it could create 15,000 comfortably sized small homes, adding new residential space to neighborhoods that are already built up.

If not used for housing, roofs could be used to add more green space to the city, which can help combat the urban heat island effect, foster biodiversity, improve air quality, and store surplus rainwater during storms.

The designers also suggest concepts like using a rooftop space for outdoor yoga or a dog park or community workshop spaces for DIY projects. Other ideas include using roofs for bike parking, as shortcuts for pedestrians, or as potential drone delivery stations.

The book also takes into consideration the potential of rooftops to host solar panels and argues for a diversity of uses. This could include cases where different uses could happen on the same roof, such as green space helping keep solar panels cooler and operating more efficiently.