Petra. The Rock. The word upon which Christ built his Church — and the word from which, according to this book, Islam too was born.In this audacious study, Hüseyin Doğan reads the Quran with christological eyes, tracing two ancient symbols through both traditions.First, the Rock. From Peter — the petra on which the Church was founded — to the cleft stone of revelation, from the Kaʿba to the face of God. The Rock stands firm: the foundation that power can name and govern.Then the fish and the letter Nūn (ن). The most hidden sign of early Christianity was not the cross, but the fish — ΙΧΘΥΣ, the Greek acrostic for "Jesus Christ, Son of God, Savior." Doğan traces this current through the prophet Jonah and the "fishers of men" into the Qur'an imagery of flowing water. Where the Rock is the foundation, the Nūn is the living, hidden faith that cannot be pinned down.Between stone and water, Petra and Nūn, a surprising reading unfolds: not a history of opposition between Islam and Christianity, but of a hidden kinship, a shared grammar of faith beneath both.An invitation to read anew what seemed familiar — for those who dare to break the stone and see what the texts truly say.