Only the seating that was extended, not the arena itself. The latest excavations indicate that it was a two-tiered structure, capable of accommodating between 8,000 and 10,000 spectators. Its size has been used as an indicator of Deva's large civilian population, and of the presence of wealthy citizens. The second phase of building is the largest known military amphitheatre in Britain. It is a protected as a Scheduled Ancient Monument. The amphitheatre served a variety of purposes. As it was close to the fortress, it would have been used as a venue for weapons training as well as hosting spectacular entertainments involving acrobats, wrestlers, and professional gladiators. The walls of the amphitheatre were thick and may have stood as high as . The buttresses were too insubstantial to be structural, so must have been decorative. Part of a slate frieze depicting a "retiarius", or net-fighter, was discovered in 1738, most likely dating to the 2nd century; it was probably used to decorate the tomb of a gladiator. Other finds included a small bronze statuette of a gladiator, parts of a Roman bowl depicting scenes from a gladiatorial contest, and part of a gladius sword handle. Much of the masonry from the amphitheatre was reused in the construction of the St John's Church and the monastery of St Mary. In 1939 some paving and the walls of two unusual elliptical buildings were discovered, one atop the other. These 'elliptical' buildings were partially uncovered behind Chester's market hall, and no similar buildings have been found in other legionary fortresses. The buildings were located near the centre of the fortress and they had their own bath buildings and a range of store rooms around the outside. The presence of a second bath building is unusual because legionary fortresses generally had just one set of internal baths. Construction on the site began around AD 77 and this was confirmed by a length of lead piping, which served a central water feature or fountain, which was stamped with the name of Emperor Vespasian. The first building was a prestigious edifice made with concrete foundations and finely dressed stonework, and was probably the finest building in the entire fortress. Technically speaking it was not elliptical, but arcuate, with the central hall being formed from two intersecting arcs, and this makes it unique in the Roman Empire. Its function is unknown. There was no seating within the arcs, which precludes a theatre, and the best guess of the archaeologists was that the twelve alcoves may have contained images of the gods, with the temple being dedicated to the twelve primary gods of the Roman pantheon.