It was built by the Romans. Sections with granite ashlars and the South Gate, or Gate of the River(Rio), now known as the Arch of Cristo have been conserved from this era. It was rebuilt by the Almohades, as testified by the use of masonry in the walls and the compacted earth in the towers. You can still see many of these defences today. Of the other three Roman entrances in this huge perimeter wall two have disappeared – the Gates of Coria and Merida – and the other was converted into the Archa of the Star(Estrella). At the same time new access points were opened, such as the Postigo (wicket gate) of Santa Ana. The wall maintains its rectangular structure, crossed by the two main streets – Cardus and Decumanus – adapted to the relief of the ground. The junction of both, the Roman Forum, is in the present-day Plaza of Santa María.