>>1734418That inner space was designed as a retail space from the start. Those little huts are supposed to be shops. The whole first three floors of that 50.000m2 building were built as a mall in the 70s. The low-rise buildings facing the street are office space and those facing the river are apartments. The towers are mixed use.
As for the structural stability, the thing was built to be tunneled under and to have a metro station in the northern half of the -2 level underground parking.
Currently the retail portion of the building, a majority of the office space, and some apartment buildings are abandoned.
I found this architectural sketch and annotated it in for more information. I coloured that green path green so you can see it.
