The flush floor finishes across the tracks allow the interior courtyard to become part of the internal living spaces when the doors are open, effectively extending the properties useable living areas. Description from iqglassuk.com. I searched for this on bing.com/images
Smithsonian National Museum of African American History and Culture :: " symbolized by the memorial space – the “oculus” – that brings light diffused by a cascade of water into the contemplative space from the Monument grounds." "An oculus, circular window, or "rain-hole" (Latin: compluvium) is a feature of Classical architecture since the 16th century."