Distance view of the Mithraeum. From: Flickr. By Pascal Lemaire, 2019.
A Mithraeum was discovered during the 1975 excavations of a Roman villa at Vulci.1 The finds included two tauroctonies, a Cautes, a raven, and other statues and altars. The tauroctonies can be dated to the first half of the third century, and the destruction of the Mithraeum to the last quarter of the 4th century.2
The second tauroctony is smaller, and the right foot of Mithras is visible in it, unlike the larger. The rear of the piece is a carved rocky surface, representing the cave.
The finds are held at the Castello della Badia museum at Vulci.3
The second mithraeum is at Vulci in Etruria and was discovered in excavations beginning in 1975.
A preliminary description has been given by A.M. Sgubini Moretti (1979).
A remarkable feature of this mithraeum is the elevation of the benches, to a height of more than a metre, on arches. On each side a row of six of these arches is flanked by two small square niches. A third niches is set in the centre of the SW bench, with three arches to each side and a smaller arch in the corresponding position on the opposite bench. Rightly, Sgubini MOretti compares this structural feature with the mosaics of Sette Porte and Sette Sfere at Ostia as a further - and most significant - example of the use of celestial symbolism within the mithraeum (p. 266 f.) However, it is unlikely, given the much smaller size of the central openings, that each bench represents the seven planetary spheres. More probable is Gordon's suggestion (MM p.277) that the twelve large arches together represent - and perhaps held images of - the signs of the zodiac and that the two central openings represent the gates of heaven. The sculptures discovered at Vulci include two fine but fragmentary statues of the tauroctony (the back of the smaller is carefully worked so as to suggest the rocky setting of the cave) and a most curious Cautes. On the back of this last is a ladder of seven arcs, ostensibly the folds of his cloak but too regular and quite unlike the natural fall of fabric. It recalls the arches of Sette Sfere, and the symbolism is surely the same - the seven celestial spheres of the
 It also in a strange way evokes the birth scene, for the rocks rise in a pile to Mithras' waist (see Pl. XIV to the article).
From vulci.it and referenced to the excavation report:
The mithraeum, a place of worship, was discovered in 1975 during excavations in an area of a home. This place of worship was found in a work room used for service. This room was long in length, with a wall at the far end, where a statue of the God Mithras was found, it had been placed there by the cult to worship. Along both sides of the room are podiums which one could step up onto by two small steps. These podiums were built upon six small arches, which are the equivalent to the number of steps one must take to reach to the seventh sphere, that of Mithras.
In the center of this long corridor room, is a small altar used for sacrifices, still intact. The altar is made of nenfro stone, on which small animals were probably sacrificed while this cult worshipped Mithras. Also within the same surroundings were found a series of statues that date back to the 3rd century A.D. Among these was a statue of Cautes, and two statues of Mithras killing a bull. The larger of these two statues was placed in front of the altar, and the smaller one was found on a niche in the wall to the right. Both statues of Mithras were found headless, a consequence of the fact that after the 380 A.D. the Christians ransacked this place of worship and set it on fire. They deliberately destroyed any traces of this cult and their God, with intention to end this religious worship that presented competition to Christianity.
Minerva 9 (1998) mentions an exhibition of the statues from Vulci at Viterbo in the Palazzo del Comune "until 10th January". Italian Wikipedia mentions that the tauroctony on display is a reproduction; the original is at the "Museo del Castello dell'Abbadia" at Vulci. (No doubt the statuary is there).
Coordinates: 42° 25' 8" N, 11° 37' 58" E / 42.3539° N, 11.6047° E.5
Moretti, A. M. Sgubini, L. Ricciardi, N. G. Perfetti Scapaticci. Il Mitreo di Vulci : Montalto di Castro : Palazzo del Comune, 21 giugno 1997-10 gennaio 1998. Viterbo, 1998. (Exhibition catalogue) 43 p., ill. (nearly all in colour) ; 22 cm. The cover is online, if unfindable here. Go to here and search for "mitreo". Copies in Italian libraries.
See also preliminary report by Anna Maria Sgubini Moretti in "Mysteria Mithrae", 259-276.
Uberti, Marisa and Giudo Coluzzi. I luoghi delle Triplici Cinte in Italia Alla ricerca di un simbolo sacro o di un quioco senzatempo, Eremon Edition, 2008. (Unclear whether this contains anything relevant)
Raffaella Deiana, Carla Zaccheddu: "Le strutture murarie del Mitreo di Vulci: una metodologia su misura nell'indagine di un rudere", in: Cinzia Nenci (ed.), Restauro archeologico: didattica e ricerca 1997-1999, Alinea Editrice, 2001, p.65 f. Article on the structure of the walls and a methodology for quantifying ruins.
Csaba Szabo, "Mithraeum of Vulci", June 2016. Blog post.
Most information on this can be found by searching for "Il Mitreo di Vulci" and "vulci mitreo". There seems very little information available in any language but Italian, and that mostly inaccessible offline.
Website at Canino.info, retrieved 5 Mar 2014: "Le sculture, della prima metà del III secolo dC, forniscono un importante termine cronologico per la datazione del complesso. Lo scavo ha evidenziato i segni di una distruzione violenta del mitreo, avvenuta intorno all'ultimo venticinquennio del IV secolo dC, molto probabilmente da porre in relazione con l'Editto dell'imperatore Teodosio che, nel 380 dC, decretando il Cristianesimo religione di Stato, di fatto vietava tutte le altre forme di culto."