PRE-NERONIAN TYPE X AND RELATED MASONRY (ROOMS 65–80)
The Type X project is the most problematic and controversial phase in the Esquiline Wing (Figs. 11 and 12). It ought not be, however. Missing or encrusted facing means that Type X cannot be described in detail as a masonry type, but the chronological position of the Type X project relative to the other phases in the Pentagonal Court is unambiguous. Type X is a distantly pre-Neronian construction, reused by Severus and Celer to form all of the Northwest Group (Rooms 65–70) of their Pentagonal Court and the west half of the North Group (the North Group is Rooms 71–83; the Type X part is Rooms 71–74, 76 and the west half of Room 80, as indicated on Fig. 11).
The masonry details are described later, but because the Type X phase is controversial, an emphatic summation of what the data tell us about it may be useful from the outset. The Type X remnant provides two sides of the Pentagonal Court, the largest and externally most distinctive design feature in the Neronian palace (the Pentagonal Court). Given that, it must seem that the Type X was an integral part of the Neronian design and must perforce have been built as part of the Neronian project. This is false; the Type X segments were reused by Severus and Celer, not built by them.