The primitive gate of Avis is one of the oldest gates of the medieval wall, being its first known record of the mid-fourteenth century. This old gate was sealed after 1806 and open again in 1967. The new gate was opened in 1804, as established by the inscription in marble, existing on the outside.
In the clear span of the original bow there were life-size frescoes of St. Sebastian, St. Anthony, Our Lady of Espinheiro and the scene of the escape from Egypt. Subjacent, about 1482, according to tradition, was founded the hermitage of Nossa Senhora do Ó, that suffered irreparable damage caused by the bombing of the city during the 1663 sieges.