This Work is an introduction to the world of symbols of the early age of Christianity, taking into consideration each “visual” symbol and not those expressed only in oral or literary form. This book deals with symbols painted in fresco or made with various techniques, mosaic, carving and engraving on different materials, but also symbols clearly recognizable in architectural shapes and in the organization of space. Before Christianity was officially accepted in the Roman Empire reaching then a privileged status, symbols concerned mainly burials, for which Romans were liberal enough to grant them to anyone. Starting with Constantine and the creation of churches and baptisteries, Christian symbols accompanied peoples for their whole life. Since the very beginning, symbols expressed the novelty brought by the new religion: the risen Christ and the Saviour of Man, a very important message already expressed in the catacombs where the main topic was salvation and immortality. Since Christ became man, every human expression and every cultural symbology could then be assumed by Christians: while Christ becomes the main subject of symbolic reflection and progressively the essential passages of the Ancient and New Testament are represented, at the same time also the whole nature, the cosmos, the animal and vegetable world, the cultural and domestic environment as well as numbers, letters and geometrie figures, though maintaining various traditional meanings, become effective symbols for expressing the Christian view about life and things. Consequently this volume, while focusing in the first three chapters on symbols of Christ, the Ancient and the New Testament, provides a view not only limited to the symbological features of the Scriptures, but deals with all those symbols connected to daily and social life as well as the relationship between nature and cosmos. The works of art and the symbols mentioned in this Work and reproduced in full colour make up most probably the widest iconographical synthesis for an introductive text as this one.