How did the pendentive improve on earlier methods of supporting domes?

Before the development of the pendentive, early monumental domes required heavy, continuous walls for support because the dome exerts thrusts around its entire perimeter. These solid walls were restrictive, as they permitted few openings and made it difficult to integrate domes into complex, multi-room structures.12

The pendentive improved upon these methods by allowing architects to raise domes on piers rather than walls. By using four inverted, spherical triangular masses of masonry, the pendentive effectively transitions a square or cubic base into a circular foundation for the dome. This innovation offers several advantages:12

• Structural Efficiency: The apexes of the pendentives rest on four piers, which conduct the forces of the dome downward, removing the need for massive, unbroken walls.12
• Spatial Flexibility: Because the dome is supported by piers, architects could create openings in the four faces of the cube, allowing for light and communication from multiple directions.12
• Architectural Integration: This method enabled the successful placement of domes over rectangular or polygonal spaces, a significant advancement over earlier techniques that were limited to round or simple structures.32