El Jem's fame comes from the amphitheatre of ancient Thysdrus. Thysdrus was a thriving market town that grew into a major junction of many major trade routes. From this wealth came their colosseum in 238 AD. This amphitheatre is the 3rd largest in the empire. At 138m long and 114m wide it is nearly as big as the one in Rome. Unlike the one in rome it is made mostly from sandstone quarried from Sullectum 30km away. It is estimated to have been able to hold 30 000 spectators.