Turicum was a Gallo-Roman settlement at the lower end of Lake Zurich, and precursor of the city of Zurich. It was situated within the Roman province of Germania Superior and near the border to the province of Raetia; there was a tax-collecting point for goods traffic on the waterway Walensee–Obersee-Lake Zurich–Limmat–Aare–Rhine.

Neolithic pile dwellings were located in the then swamp area between Limmat and Lake Zurich around the present Sechseläutenplatz plaza. These were built on piles to protect the inhabitants against occasional flooding by the rivers Sihl, Linth and Jona. Three settlements were located in Enge, a locality of the municipality of Zurich: Zürich–Enge Alpenquai and Kleiner Hafner on then islands or peninsulas on the effluence of the Limmat, and Grosser Hafner, as well as the settlement Kleiner Hafner near the present Sechseläutenplatz plaza on the effluence of the Limmat on Lake Zurich lake shore, all within an area of about 0.2 square kilometres (49.42 acres) some 500 metres (1,640 ft) away of the core of the Celtic Oppidum respectively the Roman era Vicus.

Probably in the first 1st century BC or even much earlier, the Celts settled on and around the Lindenhof hill. For the 1st century BC La Tène culture, archaeologists excavated individual and aerial finds of the Celtic Oppidum whose remains were discovered in archaeological campaigns in the years 1989, 1997, 2004 and 2007, and also the 1900s and 1930s finds which mistakenly were identified as Roman objects. Extraordinary are the single finds of 1890 at the Prehistoric pile dwelling settlement Alpenquai – the so-called Potin lumps whose largest weights 59.2 kilograms (131 lb) consist of about 18,000 of used Celtic coins which date to around 100 BC. Initially prejudged just as melt coins, the present scientific research assumes that the melting down of the lump was not completed, therefore the aim was to form cultic offerings. The site of the find was at that time around 50 metres (164 ft) from the present Bürkliplatz plaza in the Lake Zurich. Grosser Hafner was also an island sanctuary of the Helvetii in connection with the settlement at the preceding Oppidi Uetliberg and Lindenhof.

The core of the Helvetic and Roman settlement was the Lindenhof hill in the present Altstadt of the modern city of Zurich. The moraine hill was the site of the prehistoric settlements where the modern city has developed. The hilltop area dominates the city of Zurich alongside the eastern Limmat riverbank, and its northern slope called Sihlbühl towards the former Sihl delta marked the northern boundary of the Helvetic and Roman settlement – where the structures of the medieval Oetenbach Nunnery, Waisenhaus Zürich and later the Urania Sternwarte were erected at the present Uraniastrasse, and therefore important historical archaeological excavations never were done. To the south, at the St. Peter church hill, there was another cultic construction towards Münsterhof, and in the west the settlement was bounded by the present Rennweg–Bahnhofstrasse lanes and the Münzplatz plaza.

The largely flattened Lindenhof area elevates at 428 metres (1,404 ft) above sea level, and rises about 25 metres (82 ft) above the level of the Limmat at the Schipfe–Limmatquai area in the west; probably some Roman buildings were built at the site of the Zunfthaus zur Zimmerleuten on the other riverbank, and the Roman settlement may stretched towards the present Münsterbrücke which is crossing the Limmat between Grossmünster (remains of graves) and Wasserkirche, and the Münsterhof plaza.

The earliest record of the town's name is preserved on the 2nd-century tombstone found in 1747 AD on the Lindenhof hill, referring to the Roman Vicus as "STA(tio) TUR(i)CEN(sis)" as customs station for goods going to and coming from Italy at the same location as the Celtic Oppidum. The Vicus was founded probably around 15 BC, but there are no written sources. The Roman settlement first belonged to the province of Gallia Belgica, and to Germania Superior from AD 90. Roman Turicum was not fortified in the beginning, but there was a small garrison at the tax-collecting point, downstream of the lake respectively Limmat nearby the Münsterhof plaza where the goods were loaded between small river boats on the Limmat and larger ships on Lake Zurich for the transport on the water route.

Commercial and residential buildings were erected in the vicinity of the Lindenhof hill, in later times, Villae rusticae were established in the present suburban districts. At the present Zunfthaus zur Zimmerleuten at Limmatquai opposite of the Lindenhof hill, the area was stabilized with embankments; some of these mounds date back to the Roman settlement era. Due to its location on Lake Zurich lake shore at the effluence of the Limmat, where the goods had to be reloaded onto riverboats, and although Turicum was not situated alongside an important Roman main road, the water route was essential for the Roman army in the present Western and Northeastern Switzerland. Not yet archaeologically proven but suggested by historians, the very first construction of the present Münsterbrücke Limmat crossing was built in the Roman era, when the present Weinplatz square was the former civilian harbour of the Celtic-Roman Turicum, and so the term Weinplatz (literally wine plaza) has an ancient meaning.

As a Vicus, Turicum was not secured by town walls, but the buildings grouped around the customs station (Quadragesima Galliarum) where the clearance of goods and travelers prior to transfer between the provinces of Gallia Belgica and Raetia took place, mainly on the water route (from and to the Roman heartland over the mountain passes of the Swiss Alps) Walensee-Obersee-Lake Zurich passing Centum Prata (Kempraten) towards the Limmat, Aare and Rhine. Goods and travelers, probably also towards Vitudurum (Winterthur), were handled at the Vicus before crossing the Roman provinces of Gallia Belgica and Germania Superior, and transferred on the Roman road between Vindonissa (Windisch) probably via Irgenhausen Castrum and Curia Raetorum (Chur). In Turicum a duty of 2.5% (Quadragesima Galliarum) was levied.