They created a tree-like structure around an existing concrete column, with book shelves and benches for reading and relaxing.
Wooden 'branches' were constructed around the column, and the ceiling panels were painted in different shades of green.
Other requirements of the brief included a meeting place, library and leaflet display cases.
Here's some more information from OD-V
Interior by Onno Donkers (OD-V)
The Department of Art & Culture, Rotterdam sought a design for the public space of the new premises at 6 Coolsingel.
The space consists of a 40 metre long hallway with a 10 metre square space at the end.
The requirements for the interior were lounge-areas, meeting-spaces, a little library, and leaflet display cases.
The hallway was designed with an industrial approach, while the square space has more of a “nature”-touch.