You could see through the Twin Towers during their construction
Unless you work in construction, it is not common to get to see the innards of giant skyscrapers. However, catching them before the rooms and other inner structures are put in place can make the buildings see-through. This photo shows the core structure of the Twin Towers before they were completed.
The snap was taken in 1970 when they were under construction. That is why the sun can shine through. It is weird to think about the tragic end that awaited them only thirty years later. Nobody could have ever imagined that something as dreadful could happen.