Construction of a new boathouse on the Rhine in Kaiseraugst, outside Basel, Switzerland, has revealed the remains of a previously unknown Roman amphitheater that is the youngest that has ever been found in the Empire. Aaargau Canton archaeologists started excavating the site last month expecting to encounter material remains from a quarry that was abandoned in Roman times. They were surprised to find an oval ring of walls instead.
The walls encircle a hollow of the abandoned quarry and are about 165 feet long and 130 feet wide. A large entrance gate flanked on each side by smaller entrances was unearthed on the south side. A sandstone block from the threshold of another gate was found on the west side. Some of the walls have surviving plaster on the interior. Of the wooden bleachers only the impression of wooden posts they were built on remain.
The structure was adjacent to the Castrum Rauracense, the military fort built near the city of Augusta Raurica in around 300 A.D. when the Roman 
army had to redraw its defensive lines after the loss of Upper Raetian Limes in the Germanic invasions at the end of the 3rd century. The location next to the fort, the use of the abandoned quarry and the building materials use all point to the amphitheater having been constructed in the 4th century, which makes it the youngest known.
The good folks of the Basel Rowing Club will benefit greatly from this find. The plans for the boathouse have been redesigned to include the amphitheater’s remains. They will be left in situ, protected by a barriers while the new building is erected above them creating the coolest boathouse of all time.
There seems to be already an existing amphitheater, an arena that features a full circle (hence, “amphi”), at 47° 31′ 46″ N, 7° 43′ 13.21″ E – i.e. this one:
upload.wikimedia.org/wikipedia/commons/2/25/Kaiseraugst_AG_2012-09-09_Mattes_Batch_(14).JPG
A reconstruction of the town is the one here down below. Note the port area, where the Ergolz river flows into the Rhine and a few Roman patrol boats are docked –Notably, totally unprotected against the nasty savages from the other side of the river!!!. That is basically, where the new, previously unknown round structure was found:
upload.wikimedia.org/wikipedia/commons/6/66/Augusta_Raurica_Stadtrekonstruktion_Bluetezeit_240_Zeichnung_Markus_Schaub.jpg
Hence, the Rhine back then made that slope that is still visible today and the town was larger as indicated, with yet another amphitheater, or, the Rowing Club members of today maybe wont have to carry their boats any longer, but instead would use the –one and only, and even cooler– boathouse that harbors an ancient military Roman naval hub! :boogie:
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PS: Check egea-ev.de/projekte/ (project description in German), where a Roman ‘Navis’ or patrol boat was rebuilt, the reconstruction dubbed “Fridericiana Alexandrina Navis”, to be seen in action here:
youtube.com/watch?v=5m9WdOVg75E
OK, it remains to be seen if a ‘Navis’ would fit into the round structure, but the “model for the F.A.N. were two Roman wrecks discovered in the 1990s in Oberstimm near Ingolstadt and exhibited in Manching. They date from 100 AD and sailed as patrol and convoy boats in the waters of central Franconia and along the Danube for border control and defense,
Dimensions and technical data: 15.7-16 m long, 2.7 m wide; 70 cm draft, with 18-20 oarsmen, each seated 89 cm behind the other. The speed was up to 6 knots, with sail and under wind even faster”.
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:hattip: