THE PERFECT number… and some architectural features found in the Pantheon.
Oculus
A round or eye-like opening or design
Perfect number
A whole number whose summed factors equal it (6,28,496,8128)
Rotunda
Any building with a circular ground plan, and sometimes covered by a dome
Scoria
A low-density, lightweight volcanic rock
Groundmass
The compact, finer-grained material in which the crystals are embedded in a porphyritic rock (groundmass also called matrix)
Aphanitic
Fine grained
Porphyry
An igneous rock consisting of large-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate rich, generally aphanitic matrix or groundmass
Digital Citizen 