<P> The horseshoe arch (Spanish: arco de herradura / ˈarko de eraˈduɾa /), also called the Moorish arch and the keyhole arch, is the emblematic arch of Moorish architecture . Horseshoe arches can take rounded, pointed or lobed form . </P> <P> Horseshoe arches are known from pre-Islamic Syria, where the form was used in the fourth century CE in the Baptistery of Mar Ya'qub (St. Jacob) at Nisibin . However, it was in Spain and North Africa (where it went from Spain) that horseshoe arches developed their characteristic form . Prior to the Muslim invasion of Spain, the Visigoths used them as one of their main architectural features, which may come from at least the Roman period . Some tombstones from that period have been found in the north of Spain with horseshoe arches in them, with speculation about a pre-Roman local Celtic tradition . Also, the arch of the Church of Santa Eulalia de Boveda--part of a previous Roman temple--in Lugo, points in that direction . </P>

Horseshoe arches were an important architectural feature of the