Somewhere in the neighbourhood was the prison, known as the Prison of St. Diomed. In it, Pope Martin I. was detained by the Emperor Constans in 654;[986] and there Maria, the wife of Manuel Comnenus and mother of Alexius II., was confined by the infamous Andronicus Comnenus.[987] The last tower in this line of fortifications, situated on a small promontory commanding a wide view of the Sea of Marmora, is a very striking and picturesque object. It has four stories, and is constructed mostly of large blocks of marble. To it was attached a two-storied building, forming, with the tower, a small château or castle at this point. Only the foundations of the western and northern walls of the building are left, but the eastern wall, pierced by two tiers of small windows, and ornamented with string-courses, stands almost intact. The castle must have been the residence of some superior military officer. Here, some think, was the Prison of St. Diomed. In the recess of the shore immediately beyond the tower was a small postern for the use of the garrison at this point. * * * * * One cannot bring this account of the Walls of Constantinople to a close without calling to mind, again, the splendid part they played in the history of the world. To them the Queen of Cities, as her sons loved to call her, owed her long life, and her noble opportunity to advance the higher welfare of mankind. How great her services in that respect have been, we are coming to recognize more clearly, through a better acquaintance with her achievements, and a fairer judgment upon her faults. The city which preserved Greek learning, maintained Roman justice, sounded the depths of religious thought, and gave to Art new forms of beauty, was no mean city, and had reason to be proud of her record. [Illustration: Chateau and Marble Tower Near The Western Extremity of the Walls Beside the Sea of Marmora.] But never was she so grand as in her attitude towards the barbarous tribes and Oriental peoples which threatened her existence, and sought to render European civilization impossible. Some of her foes—the Goths and the great Slavic race—she not only fought, but also gathered within the pale of civilized Christendom. With others, like the Huns, Persians, Saracens, Turks, she waged a relentless warfare, often achieving signal triumphs, sometimes worsted in the struggle, always contesting every inch of her ground, retarding for a thousand years the day of her fall, perishing sword in hand, and giving Western Europe, meantime, scope to become worthy to take from her dying hands the banner of the world’s hope. This is service similar to that which has earned for Ancient Greece men’s eternal gratitude, and has made Marathon, Thermopylæ, Salamis, Platæa, names which will never die.