Numerous lake-side settlements from the Neolithic and Bronze age have been found, such as those in the Zürich Pressehaus and Zürich Mozartstrasse. The settlements were found in the 1800s, submerged in Lake Zurich. In 2004, traces of a previously unknown pre-Roman Celtic (La Tène culture) settlement were discovered (the center of which lay probably somewhat north of the Lindenhof hill, on the site of the Ötenbach monastery, removed wholesale in 1902).
The Celtic Helvetians had a settlement on the Lindenhof when they were succeeded by the Romans, who established a custom station here for goods going to and coming from Italy. The Roman vicus of Tur?cum first belonged to the province of Gallia Belgica, and to Germania superior from AD 90. Following Constantine's reform of the Empire in 318, the border between the praetorian prefectures of Gaul and Italy was just east of Turicum crossing the Linth between Lake Zurich and Walensee.
Roman Turicum was not fortified, but there was a small garrison at the tax-collecting point, set up not exactly on the border, but downstream of Lake Zurich, where the goods entering Gaul were loaded onto larger ships. South of the castle, at the location of the St. Peter church, there was a temple to Jupiter. The earliest record of the town's name is preserved on a 2nd century tombstone found in the 18th century on Lindenhof, referring to the Roman castle as "STA(tio) TUR(i)CEN(sis)".
Christianity was introduced early in the 3rd century by Felix and Regula, with whom Exuperantius was afterwards associated. According to legend, Felix and Regula were executed at the location of the Wasserkirche in 286.
The Alamanni settled in the Swiss plateau from the 5th century, but the Roman castle persisted into the 7th century. The earliest manuscript mention of the settlement, as castellum turegum, describes the mission of Columban in 610. An 8th century list of toponyms from Ravenna mentions Ziurichi. There is a legendary account of an Alamannic duke Uotila residing on, and giving his name to, the Üetliberg.