Pipes from the Neronian structure were discovered between the Piazza and the Salita dei Crescenzi. Neronian opus caementicium (concrete) has also been discovered. Brick stamps dating from the re-building by Alexander Severus were found in the remains of a hypocaust in Palazzo Madama in 1871. Another hypocaust was found on the site of San Salvatore in Thermis."Thermae Neronianae or Alexandrinae" S. B. Platner, (as completed and revised by Thomas Ashby): A Topographical Dictionary of Ancient Rome, London: Oxford University Press, 1929. pp. 531-532.
