Ninfeo di Alessandro (Trofei di Mario)

A Severan monumental fountain standing in the garden of piazza Vittorio Emanuele II, which worked both as a display fountain and as a distribution tank, a castellum aquae. Its plan is trapezoidal; it.wikipedia gives it as 25 metres wide, about 20 metres high originally, and 4,000 cubic metres. The Sovrintendenza Capitolina manages it, and the same article gives it as visitable on request, on 060608.