The Celtic hillfort of Otzenhausen is one of the biggest fortifications the Celts ever constructed. It was built by Gauls of the Treveri tribe, who lived in the region north of the fort. The first fortification was constructed in the 5th or 4th century BC, but the real heyday of construction dates to the 2nd and 1st century BC. For reasons yet unknown, the fort was abandoned shortly after this expansion.
The site is formed in the shape of a triangle with rounded ends. One rampart surrounds the whole fort. On the southern side, another similar embankment is built about 40 metres in front of the main one. The ends of this outer rampart approach the main one but do not touch it. Because the entrance of the main rampart is located on the western side, no significant purpose for the outer one has been determined. From west to east the fort extends 460 m, from north to south 647 m. The total length of the ramparts is 2500 metres and they contain 240,000 cubic metres of stone. Thousands of beams were attached to the ramparts which, as the diagram shows, probably presented a vertical stone wall to the exterior. Perhaps there was a second gate on the eastern side, but its existence is not yet proven.
In Roman time a small temple of 2.15 metres x 2.70 metres, dating from the 2nd or 3rd century A.D. was built of quartzite rubble stone and brick-shaped sandstone. When German tribes invaded the Roman territories in 4th century A.D, the fort was used again. During the Thirty Years War (1618–1648) the citizens of the surrounding villages again took refuge in the remains of the Celtic fort. Excavations took place in 1883 and from 1936 to 1939.References:
The Arch of Constantine is situated between the Colosseum and the Palatine Hill. It was erected by the Roman Senate to commemorate Constantine I's victory over Maxentius at the Battle of Milvian Bridge in 312. Dedicated in 315, it is the largest Roman triumphal arch. The arch spans the Via triumphalis, the way taken by the emperors when they entered the city in triumph.
Though dedicated to Constantine, much of the decorative material incorporated earlier work from the time of the emperors Trajan (98-117), Hadrian (117-138) and Marcus Aurelius (161-180), and is thus a collage. The last of the existing triumphal arches in Rome, it is also the only one to make extensive use of spolia, reusing several major reliefs from 2nd century imperial monuments, which give a striking and famous stylistic contrast to the sculpture newly created for the arch.
The arch is 21 m high, 25.9 m wide and 7.4 m deep. Above the archways is placed the attic, composed of brickwork reveted (faced) with marble. A staircase within the arch is entered from a door at some height from the ground, on the west side, facing the Palatine Hill. The general design with a main part structured by detached columns and an attic with the main inscription above is modelled after the example of the Arch of Septimius Severus on the Roman Forum.