This book fills in a blind spot in current architectural theory and practice, looking into a notion of conservation as a form of invention and imagination, offering the reader a counter-viewpoint to a predominant western understanding that preservation should be a 'still shot' from the past. Through a micro-historical study of a Renaissance concept of restoration, this book provides a theoretical framework to question the issue of conservation as a possible creative endeavour, when a mnemonic building is concerned, entailing conservation of memory within changes. It focuses on Tiberio Alfarano's 1571 ichnography of St. Peter's Basilica in the Vatican, into which was woven a complex body of religious, political, architectural and cultural elements.