<p>Large open space — not a formal <i>circus</i> — in the SW *Campus Martius, between the *Theatrum Marcelli and the Temple of *Mars, and oriented along the NW axis of the road which led to the *Tiber (*Via Tecta [1]) and beyond that, to Veii (*Via Triumphalis). The area was topographically significant since it gave its name, sometime after the Augustan era, to <i>Regio IX: Circus Flaminius</i> (<i>Reg. Cat.</i>; s.v. *Regiones Quattuordecim). The Circus Flaminius occupied the <i>prata Flaminia</i>, property donated to the people of Rome in 221 B.C. by C. Flaminius (perhaps as a victory monument?; Livy 3.54.15; <i>Per.</i> 20; cf. Plut., <i>Quaest. Rom.</i> 66); however, the original property may not have corresponded exactly to the later extension of the circus (Viscogliosi). According to mediaeval accounts, the Circus Flaminius was located in the *Campus Martius S of the *Porticus Minucia and N of both the *Porticus Octaviae and *Porticus Philippi (Marchetti-Longhi 127-29). In the Renaissance, Pirro Ligorio erroneously identified the Circus Flaminius with the remains in Via delle Botteghe Oscure that would later reveal themselves as the *Theatrum of Balbus. In 1960 Gatti, after analyzing the ancient written sources and an account by Albertini, relocated the Circus Flaminius S of the *Porticus Octaviae (contra, Marchetti-Longhi 122-27). The join between the fragment of the Severan Marble Plan depicting the Porticus Octaviae and the *Porticus Philippi (Rodríguez Almeida, <i>Forma</i> pl. 23, frag. 31cc) and the fragment inscribed CIR[CVS] FLAMI[NIVS] (frag. 30) made Gatti’s relocation undeniable. As a consequence, the placement of all the temples known to be <i>in Circo</i> required revision, as well as the theory (originally postulated by von Domaszewski and later taken up by Castagnoli) that the water-course known as the *Petronia Amnis formed the NW boundary of the Circus Flaminius, since the circus extended to the NW part beyond that point.</p> <p>The strong triumphal character of the Circus Flaminius is stressed by the high density of sacred structures (most of them victory monuments) — either identified through archaeological remains or mentioned in ancient accounts — that cluster around it and define its boundaries. While it is generally assumed that the long sides of the Circus were monumentalized by temples, there is no evidence that any sacral buildings other than the Temple of the *Dioscuri delimited the SW side. In fact, the Marble Plan from the Via Anicia (cf. *Castor et Pollux, Aedes) shows commercial <i>horrea</i> (warehouses) flanking the temple.</p> <p>Known to have been <i>in Circo</i> were the temples of Iuppiter Stator and Iuno Regina (enclosed in the *Porticus Metelli–Octaviae), the temple of Hercules Musarum within the *Porticus Philippi, the temples of *Mars, the *Dioscuri, *Pietas, *Diana, *Fortuna Equestris, and *Hercules Magnus Custos. The temples of *Bellona, *Apollo Medicus, and *Neptunus, all located along the edge of the circus, are described by ancient sources both as <i>in Circo</i> and <i>in Campo</i>; these monuments follow the strict N–S orientation common to structures in the Campus Martius, and their cults probably were established before the monumentalization of the Circus Flaminius (Viscogliosi).</p> <p>A precise chronology for the construction of these temples is unavailable; the shape of the region seems to result from spontaneous and intense urbanistic encroachment rather than a short-term building campaign. Coarelli proposes a relative chronology based upon the foundation dates of the temples (1968, 308), yet these remain under debate and Coarelli’s chronology awaits archaeological confirmation.</p> <p>The description ‘<i>in circo Flaminio</i>’ first appeared in accounts of the Augustan period, having only a general topographical meaning rather than designating a specific area (Zevi 1052; Olinder 17-24, 51). The rather late development of this terminology suggests that the Circus Flaminius began to be considered a topographic landmark only as temples and porticoes were built around it, defining its boundaries. For this reason Wiseman (4) hypothesized that the Circus Flaminius was not a conventional circus designed for horse-racing, but rather the term ‘<i>circus</i>’ referred simply to its round shape (note that the *Trigarium served as racetrack through late antiquity). In fact, the Circus Flaminius served many purposes beyond horse races, often hosting markets, assemblies (<i>contiones</i>), or games (<i>ludi</i>), as well as serving as an important staging ground for triumphal parades before they entered the territory of the city proper (Livy 39.5.17, 45.39.14; Plut., <i>Luc</i>. 37.2; *Porta Triumphalis; *Triumphal Way [Extramural]). It seems the borders were never rigorously defined; at least, no archaeological remains that could be interpreted as stands or a barrier have been recovered. This openness allowed for both races and commercial activities in the circus (Zevi 1049). In the Augustan period the Circus Flaminius was paved and its large open area was used only on specific occasions (<i>lustra</i>), such as the <i>ludi Plebeii</i> (Val. Max. 1.7.4; Livy 2.36) and <i>ludi Taurii</i> (Varro, <i>Ling.</i> 5.154) as well as some occasional games (Dio Cass. 55.10.8: the <i>venatio</i> of Augustus in 2 B.C.; La Rocca 105). Thus, as early as the first principate, the Circus Flaminius was an expansive gathering place whose use involved everyday activities more similar to a forum or marketplace, rather than a racing track.</p>