The Helvetii were a Celtic tribe that played a significant role in the history of pre-Roman Switzerland. According to a legend preserved by Pliny the Elder (77 CE), a Helvetian named Helico, after working in Rome, brought home figs, grapes, oil, and wine, inspiring his people to invade northern Italy. Historically, the Greek historian Posidonius (2nd–1st century BCE) described the Helvetii as wealthy in gold and peaceful, although early interpretations of their gold-washing activities in Swiss rivers, such as the Emme, are now questioned. Instead, it is believed that the Helvetii originally lived in southern Germany, as confirmed by Tacitus and Ptolemy, who noted abandoned Helvetian lands north of the Rhine.
By the late 2nd century BCE, pressured by Germanic incursions, some Helvetian groups, like the Tigurini, began migrating south into the Swiss Plateau. Around this time, the Helvetii established settlements, including the oppidum at ZĂĽrich's Lindenhof hill. A remarkable discovery from ZĂĽrich's Alpenquai involved "Potin lumps," a fused mass of 18,000 Celtic coins from about 100 BCE, suggesting a partially completed ritual offering.
Other Helvetian religious and settlement sites include sanctuaries on former islands in Lake Zurich, such as the Grosser and Kleiner Hafner sites near the Limmat's outflow. These findings reflect the Helvetii’s integration into local trade networks and cultural practices, laying the foundation for their presence in the region before Roman conquest.