The walls are of strong Roman Concrete made with pozzolanic sand and large, uniformly sized, hard selce aggregate. The internal walls are faced neatly sawn opus latericium very carefully laid with extremely hard mortar. The bricks are rendered with three layers of graded cocciopesto, coarsely graded nearest the bricks, and recoated with finer graded particles in the mixture. The final layer is very smooth and has the appearance of being mixed with powdered white marble. This in turn carries the classic vitreous caeruleum, verdigris, minium and other coloured pigments that may be seen.
Vertical Cross Section Through Nymphaeum Structure above and below ground.
Current external ground level above roofs along line A-A.
Current interior ground level in north-west and central chambers approximated along line B-B.