This book is about the Christ Pantokrator, an imposing monumental complex serving monastic, dynastic, medical and social purposes in Constantinople, founded by Emperor John II Komnenos and Empress Piroska-Eirene in 1118. Now called the Zeyrek Mosque, the second largest Byzantine religious edifice after Hagia Sophia still standing in Istanbul represents the most remarkable architectural and the most ambitious social project of the Komnenian dynasty. This volume approaches the Pantokrator from a special perspective, focusing on its co-founder, Empress Piroska-Eirene, the daughter of the Hungarian king Ladislaus I. This particular vantage point enables its authors to explore not only the architecture, the monastic and medical functions of the complex, but also Hungarian-Byzantine relations, the cultural and religious history of early medieval Hungary, imperial representation, personal faith and dynastic holiness. Piroska's wedding with John Komnenos came to be perceived as a union of East and West. The life of the Empress, a "sainted ruler," and her memory in early Árpádian Hungary and Komnenian Byzantium are discussed in the context of women and power, monastic foundations, architectural innovations, and spiritual models.