built on the Grosser Hafner island, which allows a dendrochronological dating. The building was erected in 122 AD, and consisted of oak piles driven deep into the lake bottom. It was surrounded probably with walls made of perishable materials, which formed a circle of seven meters in diameter. The rotunda is located on the former Neolithic island settlement, about away from the Roman Vicus. The archaeological material indicates that the facility was used up in the 3rd century AD, even up in the 4th century AD by the Gallo-Roman population. On the one hand, the interpretation as the temple is based on the insularity and the design, on the other hand on finds of coins; the majority of the now nearly 90 coins probably are from a so far not proven predecessor building, probably from the third quarter of the 1st century AD. There are also the fragments of bar tiles of maybe another Roman building. On occasion of diving operations from 1998 to 2001 almost of tile fragments are ensured, and up to 40 coins and several pottery shards, as well as rectangular post hole. Gallo-Roman era The Alamanni settled in probably from the 5th century when the Roman military retreated back to Italy, but the Roman castle persisted into the 7th century and was reinforced by the Ottonian dynasty, but broken around 1218 AD. To date, few archaeological remains of the Roman Zürich could be excavated systematically because the remains of the settlement are hidden under the densely built-up core of the modern city of Zürich. Archaeologically excavated are the remains of public baths (Thermengasse), graves and traces of craft enterprises, residential buildings, as well as everyday objects and jewelry, but also of cult equipment. Archaeological exploration Archaeological excavations usually were executed on occasion of renewals of present buildings at Rennweg 5/7 (settlement structures), Fortunagasse 28/Rennweg 38 and Oetenbachgasse 5–9 (Celtic trench and settlement structures), Münzplatz (settlement structures), Lindenhof hill (Celtic, Roman and medieval settlement structures), Rennweg 35 (Celtic spot plates (Tüpfelplatten) and settlement structures), the Limmat (bars) and Bürkliplatz-Bahnhofstrasse (Celtic Potin coins), all representing the Helvetii and early Roman settlement. Focussed on the Gallo-Roman era, archaeological explorations were executed at Weinplatz 3/4/5 and Storchengasse 23 (harbour area and thermae), Storchengasse 13 (cultic building) and neighbored Fortunagasse 28/Rennweg 38 (maybe a hostel) and gold jewellery at the Sihlbühl area, Poststrasse/Zentralhof at Münsterhof (probably early medieval graves), and the