If you are reading this while sitting in one of the world’s big cities chances are that you’re in a tall grey-looking building overlooking several more of them.

For Rotterdam-based architect Winy Maas, unlocking these kinds of built-up areas and creating new spaces in our overcrowded cities is one of his curiosities. Instead of rows and rows of skyscrapers, Maas says he is interested in unlocking those spaces and making them greener and more communal.

One example he showed is of a building in Rotterdam that was transformed just by adding a flight of stairs that lead from the ground floor all the way to the rooftop. That way many visitors can come to a site that was not always accessible to them. Instead the building becomes a place to hang out on the roof, take pictures or have fashion shows along the stairs and simply a way of attracting visitors to the city. Maas says a simple solution like this can work to unlock many other similar buildings in cities around the world.

Maas, of MVRDV, says he is not that interested in the current move towards open-source design, preferring instead to look at how to improve on what is already there: “I don’t care about open source. I don’t care for it. We have to use things from the past, bring it further [into the future] and develop it.”

He says that is what he, along with his PHD and master's students, spend their time thinking about. “We have built up everything. There is too many of us here. What is the alternative?” he asks.

A clever solution they came up with is to create the illusion of space in a high street by making bricks out of glass. For Crystal House, instead of bricks, the bottom half of the building is made out of glass bricks, making the high street look like something made of ice.

He says that as a result: “everyone wants to touch the building. That is what I am most proud of. I finally made a building like the Taj Mahal that everyone wants to touch.”