When I.M. Pei designed the giant shopping mall and welcome center that sits under the courtyard of the Louvre in the 1980s, he created a spectacular, and originally controversial crystal pyramid to serve as a grand entrance and three smaller ones around it.
The pyramids let light into the grand lobby, and one of the smaller ones continues underground to form a spectacular inverted pyramid in the lobby, where it admits light, creates amazing reflections, and provides a great backdrop for selfies.
Add picture of surface from older blogs.
