fornix, ĭcis, m., an arch or vault (cf.: camera, testudo, tholus, lacunar). Lit.: Democritus invenisse dicitur fornicem, ut lapidum curvatura paulatim inclinatorum medio saxo alligaretur, Sen. Ep. 90 med.: si quis in pariete communi demoliendo damni infecti promiserit, non debebit praestare, quod fornix vitii fecerit, Cic. Top. 4, 22; Auct. Her. 3, 16, 29: aqua fornicibus structis perducta (Romam), Plin. 31, 3, 24, § 41: conspicio adverso fornice portas, the entrance under the archway over against us, Verg. A. 6, 631: fornices in muro erant apti ad excurrendum, vaulted openings from which to make sallies, Liv. 36, 23, 3; a covered way, id. 44, 11, 5.—Poet., of the arches of heaven: caeli ingentes fornices, Enn. ap. Varr. L. L. 5, § 19 Müll. (Trag. v. 423 ed. Vahl.), a figure found fault with by Cicero, Cic. de Or. 3, 40, 162.— In partic.: Fornix Făbĭus, a triumphal arch built by Q. Fabius Allobrogicus in the Sacra Via, near the Regia. Cic. Planc. 7, 17; Quint. 6, 3, 67; also called Fornix Fabianus, Cic. Verr. 1, 7, 19 (for which: Arcus Fabianus, Sen. Const. Sap. 1); and: Fornix Fabii, Cic. de Or. 2, 66, 267; cf. Becker's Antiq. 1, p. 239 sq.— Transf., a brothel, bagnio, stew, situated in underground vaults, Hor. S. 1, 2, 30 sq.; id. Ep. 1, 14, 21; Juv. 3, 156; 11, 171.—Hence, transf., of one who gave himself up to prostitution: (Caesarem) Curio stabulum Nicomedis et Bithynicum fornicem dicit, Suet. Caes. 49.