The history of Constantinople--it is proclaimed at every epoch in her life--has ever its two abiding interests, the Church and the military spirit. The one is represented for all time in S. Sophia. The other finds its memorial in the walls. For centuries, whose heroic story we have so baldly told, the city of the Cæsars preserved for Europe the justice of Rome, the learning of Greece. She taught to the barbarians the meaning of _civilitas_, she led many of the nations into the truest brotherhood of the Catholic Church. And all through she was fighting a war which never ceased, often driven back upon her own defences, but again and again issuing forth a conqueror. By her age-long resistance Constantinople saved Europe from a new barbarian deluge, from a second Dark Age. And Constantinople herself was saved by her walls. There is no historic monument in Europe which has a memory more glorious or more heroic. To the student of history there is nothing of all he sees in the "Queen of Cities" that is so full of perpetual and varied interest. The whole story of Constantinople might be told in commentary on the great walls that once protected her from the foe. Here it shall only be pointed how two or three days may be spent--or two or three hours if it must be so--in learning something of these magnificent ruins which have so great a history written on their face. The writer has spent many happy hours in tracing them at every point. Within a few days of his last visit the knowledge, such as it was, which he had gained, was a hundredfold increased by the superb work of devotion and research in which Professor van Millingen has summed up the studies of many years, which will be, once for all, the classical authority on the walls and adjoining sites of Byzantine Constantinople. It has often already been referred to in these pages. Here let it be said that every word that is written on the walls is revised in the light of what Professor van Millingen has published, and that no one who wishes seriously to study the history of the fortifications, or indeed of the city itself, can now do so with any success without the help of this almost faultless book. The simplest method for the traveller is probably first to take the less interesting and more ruinous walls on the Golden Horn and the Sea of Marmora--which indeed will probably only be visited in detail by those who have a special historical interest, and then to turn to the Land walls, which no one ever visits the city without seeing at least in superficial view. [Illustration: KADIKEUI (CHALCEDON), FROM SERAGLIO POINT]