<p>Naval arsenal, with rows of warship sheds, along the *Tiber bank of the SW *Campus Martius, stretching opposite the transtiberine <i>prata Quinctia</i> (Livy 3.26.8: <i>contra eum ipsum locum ubi nunc navalia sunt</i>; s.v. *Trans Tiberim) and thus upstream from the *Insula Tiberina (Richardson; Coarelli 1997, 348-49), but not too far away from the city walls since the <i>porta Navalis</i> was ‘in the vicinity of the Navalia’ (Festus 187; puzzled about the topographical implications: Richardson). No remnants are known, unless a sizeable portico of the Republican period belonged, in some way, to the facilities (tentatively, Coarelli 1997, 349; *Porticus: Vicus Aesc(u)leti). The Navalia complex was already fully established by the 3rd/2nd c. B.C. (Livy 8.14.12, 40.51.6), with additional work carried out in the later 2nd c. B.C. by the prestigious architect Hermodoros of Salamis (as Cic., <i>De or.</i> 1.62, implies). The naval arsenal was in regular use when Cato the Younger returned from his Cypriot mission in 56 B.C. (Plut., <i>Cato Min</i>. 39.2: εἰς τὸ νεώριον). Its buildings could also be used to keep wild animals until needed in circus games (Pliny, <i>NH</i> 36.40, for the time of Pompey). They were damaged by lightning in 44 B.C. (Obsequens 68). The testimonies of Livy (3.26.8) and Pliny (<i>loc. cit.</i>), both of whom use the <i>navalia</i> as an unqualified point of reference during their lifetimes, contradict the inference of Coarelli (<i>LTUR</i> III, 340) that the arsenal had fallen out of use by the mid-1st c. B.C. Moreover, Procopius’ 6th-c. A.D. eyewitness account of a ‘ship of Aeneas’ faithfully preserved in a shipshed ‘in the middle of the city along the Tiber’ seems to apply to the Navalia (<i>Goth.</i> 4.22.7-8 = <i>De bell.</i> 8.22.7-8; Coarelli 1997, 347-48; Tucci 39-40; with reservations, Richardson).</p> <p>The Marble Plan fragment from Via Anicia (perhaps of Augustan date, Coarelli 1997, 507; Tucci 37; contra, Conticello de’ Spagnolis 59, who favors the first half of the 2nd c. A.D.) shows part of an edifice situated along the Tiber bank near the Temple of *Castor and Pollux in the SW Campus Martius (Rodríguez Almeida, esp. 127 fig. 5); the structure also appears on the Severan Marble Plan (Rodríguez Almeida 121 fig. 1, frag. 32i) and has been connected with the Navalia (Conticello de’ Spagnolis 53; Tucci). Tucci advocates an intriguing identification of Procopius’ “ship museum” with the building depicted on the ancient plans, which he characterizes as a special shipshed arranged parallel, rather than perpendicular, to the river (40-41; id. 38-39 for other explanations, such as Rodríguez Almeida’s <i>statio alvei Tiberis</i>, seat of the Tiber administration). Yet this connection is based on a variety of assumptions; it is not even clear whether the edifice can be attributed to the Augustan building activities in the Circus Flaminius area, as Tucci suggests (40).</p> <p>Our map assigns an index number to the Navalia and places it near the presumed center of the arsenal at a stretch of the Tiber by the *Circus Flaminius where its banks were sheltered from the direct impact of currents (a situation most advantageous for launching and docking the elongated, unstable warships). The area was structured around a NW-SE thoroughfare, plausibly identified as the main road of the *Vicus Asc(u)leti neighborhood; by the time of Via Anicia plan (and documented by it), the surrounding space was clogged with a dense array of shops and commercial buildings. Further downstream, S of the *Theater of Marcellus, was the zone of the *Portus Tiberinus.</p>