Hoc brachium est beati Iohannis Baptistae : osservazioni sulla provenienza della reliquia di San Giovanni Battista conservata a Siena

Saint John's right arm, a revered relic belonging to the cathedral of Siena, presents many puzzles while it opens diverse paths of investigation. Even though the events following Pope Pius II Piccolomini's 1464 donation of the relic are well known, information about the preceding period remains elusive. Documents kept in the Archivio dell'Opera Metropolitana di Siena seem only to allow us to define the history of this relic and its reliquary before their arrival in Siena. A cross-analysis with other texts sheds some light on certain aspects of its complex and enthralling history, which extends from Constantinople to Italy, across the Balkans and the Mediterranean Sea, and relates to the history of several relics that have also been regarded as St John's right arm – especially those now in Istanbul and Cetinje (Montenegro). The collected information also allows us to develop comparisons between relics' fruition and adornment modes in Western and Eastern Europe from the twelfth century to recent times, since the numerous relics of "St John's right arms" have been preserved in extremely precious reliquaries, the shapes of which reflect different religious and cultural contexts. Furthermore, not only do these reliquaries allow us to develop, from a comparative perspective, some observations on the formal evolution of taste of the different eras of manufacture and on the evolution of the forms of devotion to saints' relics; they also serve as useful tools in investigating the relics' origins and identifying which relic is actually indicated in each medieval and early-modern testimony relating the Baptist's right arm.