Before the era of railways, the traveller in approaching Rome, across the Campagna, was generally electrified by the first glimpse of S. Peter's dome looming in the distance. Then he had full time, in advance of entering the gates of the city, to ponder over all the recollections which the magical word "Roma" might suggest to him. At present he is rapidly borne into the city, and sometimes before he is aware of having arrived even in its neighbourhood; yet the dome is plainly visible from afar by the railway approach of to-day. Now, as then, the first sight of Rome is always her unequalled cathedral; now, as then, the latter is the great object which the tourist eagerly hastens to visit. The present Church of S. Peter is relatively modern, having been first conceived by Pope Nicholas V. about the year 1450. It is built upon the site of the religious edifice erected in the time of Constantine, and consecrated as the "Basilica of S. Peter." The old basilica stood on part of the Circus of Nero, and occupies the spot consecrated by the blood of the martyrs slaughtered by order of that tyrant. Tradition supposes that the basilica held possession of the body of the apostle after his crucifixion,--a circumstance which reflected high credit upon it, and dignified its entrance with the appellation of the "limina apostolorum" (threshold of the apostles). After enjoying the veneration and tributes of all Christendom during eleven centuries, the walls of the old basilica began to give way, and its approaching ruin becoming visible about the year above stated, Nicholas V. conceived the project of taking down the old church, and erecting in its stead a new and more expensive structure. The project was begun, and resulted, after a long series of experiments made by various architects, in the splendid fabric which is now regarded by the world as the chief glory of modern Rome. The work made slight progress until the epoch of Julius II., who resumed the great task, and found in Bramante an architect capable of comprehending and executing his grandest conceptions. The walls of the ancient basilica were then wholly removed, and on the 18th of April 1508 the foundation stone of one of the vast pillars supporting the dome, as we now see it, was laid by Julius with great pomp and ceremony. From that period the work, though carried on with ardour and perseverance, continued during one hundred years to occupy the attention and absorb much of the incomes of eighteen pontiffs. The most celebrated architects of the times displayed their talents in its erection--namely, Bramante, Raphael, San Gallo, Michael Angelo, Vignola, Carlo Maderno, and last, though not least, Bernini, who gave it the finishing touches of ornamentation, and who built the enclosing colonnade. It is estimated that its cost, after completion, was no less than £12,000,000 sterling--a sum representing a far greater value than it does in our day.