Irgenhausen Castrum is a Roman fort situated on Pfäffikersee lake shore. It was a square fort, measuring 60 metres in square, with four corner towers and three additional towers. The remains of a stone wall in the interior were probably a spa.
In the Roman era, there was a Roman road from Centum Prata (Kempraten) on Obersee–Lake Zürich via Vitudurum (Oberwinterthur) to Tasgetium (Eschenz) on the Rhine. To secure this important transport route, the castrum was built. The native name of the fort is unknown: Irgenhausen was mentioned in AD 811 as Camputuna sive Irincheshusa, so maybe the castrum's name was Cambodunum, the Roman name of the neighboring village of Kempten.
For the dating of the fort there are two theories: the first assumes that the fort was built at the time of the Emperor Diocletian around AD 294/295. The other theory, based on the Roman coins found inside the castrum, dated the construction from 364 to 375, in the era of the Emperor Valentinian II. As early as AD 400 the castrum was evacuated and destroyed by Alamanni invaders.
In addition to the remains of the towers and surrounding wall, there were found the remains of stone interior buildings: a three-roomed building was seen as a spa. Another building with three rooms has been interpreted as principia, the headquarters of the fort. At the southern corner tower a hypocaust system of an older villa rustica from the 1st to the 3rd century was excavated. The other buildings were made of wood and therefore cannot be individually identified. However, some military barracks, a horreum and a praetorium was probably built inside the fort. In the middle of the hill there was a sunken room. Most of the relics found inside the fort date from the 2nd and 3rd centuries AD and are thought to be relics of the villa rustica on whose ruins the fort was built. At the present time, a red ribbon in the wall shows where the Roman wall ends and the restored wall begins.References:
Roman Walls of Lugo are an exceptional architectural, archaeological and constructive legacy of Roman engineering, dating from the 3rd and 4th centuries AD. The Walls are built of internal and external stone facings of slate with some granite, with a core filling of a conglomerate of slate slabs and worked stone pieces from Roman buildings, interlocked with lime mortar.
Their total length of 2117 m in the shape of an oblong rectangle occupies an area of 1.68 ha. Their height varies between 8 and 10 m, with a width of 4.2 m, reaching 7 m in some specific points. The walls still contain 85 external towers, 10 gates (five of which are original and five that were opened in modern times), four staircases and two ramps providing access to the walkway along the top of the walls, one of which is internal and the other external. Each tower contained access stairs leading from the intervallum to the wall walk of town wall, of which a total of 21 have been discovered to date.
The defences of Lugo are the most complete and best preserved example of Roman military architecture in the Western Roman Empire.
Despite the renovation work carried out, the walls conserve their original layout and the construction features associated with their defensive purpose, with walls, battlements, towers, fortifications, both modern and original gates and stairways, and a moat.
Since they were built, the walls have defined the layout and growth of the city, which was declared a Historical-Artistic Ensemble in 1973, forming a part of it and becoming an emblematic structure that can be freely accessed to walk along. The local inhabitants and visitors alike have used them as an area for enjoyment and as a part of urban life for centuries.
The fortifications were added to UNESCO"s World Heritage List in late 2000 and are a popular tourist attraction.