Blood and Gold. Mystery and Wonder. These have been the keys to understanding the profound soul of Naples throughout the centuries. And there is something that has managed to encompass all of this: the miraculous relics of blood. That of San Gennaro, certainly. But not only his, because the city, throughout its history, has been adorned with dozens, hundreds of relics of blood, to the point that in the 18th century a French traveler, astounded by their number, referred to the city as Urbs Sanguinum, the city of blood. And among them, some have challenged common sense and the laws of creation for hundreds of years. And they still do today. This book is a journey into the unfathomable and incomprehensible mystery of the relics of blood that miraculously liquefy in Naples. Whether believers or skeptics, it matters little. The very existence of these miraculous relics is an enigma that touches anyone in the depths of their soul.