Zürich has been continuously inhabited since Roman times. The vicus of Turicum was established in AD 90, at the site of an existing Gaulish (Helvetic) settlement. Gallo-Roman culture appears to have persisted beyond the collapse of the Western empire in the 5th century, and it is not until the Carolingian period. A royal castle was built at the site of the Lindenhof, and monasteries are established at Grossmünster and Fraumünster. Political power lay with these abbeys during Medieval times, until the guild revolt in the 14th century which led to the joining of the Swiss Confederacy. Zürich was the focus of the Swiss Reformation led by Huldrych Zwingli, and it came to riches with silk industry in Early Modern times. Early history 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 Zürich. Located on the then swamp land between the Limmat and Lake Zürich around Sechseläutzenplatz on small islands and peninsulas in Zürich, Prehistoric pile dwellings around Lake Zürich were set on piles to protect against occasional flooding by the Linth and Jona. Zürich–Enge Alpenquai is located on Lake Zürich lakeshore in Enge, a locality of the municipality of Zürich. It was neighbored by the settlements at Kleiner Hafner and Grosser Hafner on a then peninsula respectively island in the effluence of the Limmat, within an area of about in the city of Zürich. As well as being part of the 56 Swiss sites of the UNESCO Worl Heritage Site Prehistoric pile dwellings around the Alps, the settlement is also listed in the Swiss inventory of cultural property of national and regional significance as a Class object. In 2004, traces of a previously unknown pre-Roman Celtic (La Tène culture) settlement were discovered, the center of which lay on the Lindenhof hill respectively the area around the Münsterhof square besides the Limmat. The Celtic Helvetians had a settlement when they were succeeded by the Romans, who established a custom station here for goods going to and coming from Italy. At the later Vicus Turicum, probably in the first 1st century BC or even much earlier, the Celts settled at the Lindenhof Oppidium. In 1890, so-called Potin lumps were found, whose largest weights at the Prehistoric pile dwelling settlement Alpenquai. The pieces consist of a large number of fused