The Roman Amphitheater of Rimini used to be one of the bigger ones in existence. It also used to be close to the sea, but the coastline has receded quite a bit since then.
Roman Amphitheater Rimini
Useful information
Address: Via Roma, 86 – 47921 Rimini. The monument can be viewed from outside.
History

The monument was constructed in the 2nd century AD. This was evidenced by the find of coin with the likeness of Emperor Hadrian found inside some brickwork.
Its position close to the water meant that it was one of the first buildings people arriving by sea used to see of the city.
In the 3rd century, Barbarians attacked the city. To be able to defend themselves, the inhabitants built a wall around the city. The amphitheater was incorporated in this wall.
In the Middle Ages it lost its original function completely. Where gladiators used to fight each other, there was now a vegetable garden.
In the 17th century, a lazaretto was built on the site.
Only in the 19th century, excavations unearthed part of the ancient amphitheater. The south-west sector has remained buried, however, since the Italian-Swiss Education Center has occupied the site since the war.
During the war, more damage was done. The wall of the arena, one of the main entrances and some access gates to the balconies are all that is left of the amphitheater.
Numbers
Rimini’s Roman amphitheater is elliptical and measures 118 by 88 meters. The actual arena is 73 by 44 meters. There was space for more than 12,000 spectators.
There were two main entrances at the ends of the main axis. Smaller entrances led to the outer corridor, from which steps led to the stone seating areas.
The outside portico was made up of 60 arches.