The collaboration between C. van Lohuizen and Th. K. van Eesteren is regarded as one of the most exemplary collaborations in the history of Dutch urbanism. Not only because of the unified commitment to the promotion of urbanism as a practice with research as its funda- ment, but perhaps more because of the acquired mythical status. What has so far remained unclear is how the collaboration of van Lohuizen and van Eesteren actually worked. Like true twins, van Eesteren and van Lohuizen used their own secret language when amongst each other. To the outside world however, van Eesteren and van Lohuizen spoke in unison, explaining each other’s view on urbanism without hesitation.

Van Lohuizen and van Eesteren were certainly not identical twins. They spent the first years in their professional career separated from each other, in complementary fields of work. Van Eesteren as an architect/artist and van Lohuizen as a civil engineer. It is however in these first years of their professional life that they independently dis- covered the importance and potential benefits of the practice of urbanism.