The use of Roman and Late-antique spolia in the erection of Umayyad infrastructures is extensively documented, from Bilad al-Sham to al-Andalus. Particularly in the latter, spolia were key in the construction of mosques, of which the Friday Mosque of Córdoba is the most paradigmatic example. The reuse of decorative and architectural materials in these religious spaces has been broadly discussed, and it has been often concluded that there were aesthetic, religious and ideological reasons, as well as strong political needs of legitimation and representation of the Umayyad dynasty. In this context, the case of the mosque of Madinat al-Zahra' is quite striking. Here, while spolia seem to have been absent, the capitals designed for its prayer room stand out for their particular characteristics, often described as resembling Visigothic models and as a product of rush. This paper aims to bring together the information available about the use of spolia in Umayyad mosques and its possible explanations, as well as to bring forward the particularities of the series of capitals designed for the mosque of Madinat al-Zahra', suggesting new ideas for their interpretation.