The distance which separated the travelers from the annular summits of Tycho was not so great but that they could catch the principal details. Even on the causeway forming the fortifications of Tycho, the mountains hanging on to the interior and exterior sloping flanks rose in stories like gigantic terraces. They appeared to be higher by 300 or 400 feet to the west than to the east. No system of terrestrial encampment could equal these natural fortifications. A town built at the bottom of this circular cavity would have been utterly inaccessible. Inaccessible and wonderfully extended over this soil covered with picturesque projections! Indeed, nature had not left the bottom of this crater flat and empty. It possessed its own peculiar orography, a mountainous system, making it a world in itself. The travelers could distinguish clearly cones, central hills, remarkable positions of the soil, naturally placed to receive the _chefs-d’œuvre_ of Selenite architecture. There was marked out the place for a temple, here the ground of a forum, on this spot the plan of a palace, in another the plateau for a citadel; the whole overlooked by a central mountain of 1,500 feet. A vast circle, in which ancient Rome could have been held in its entirety ten times over. “Ah!” exclaimed Michel Ardan, enthusiastic at the sight; “what a grand town might be constructed within that ring of mountains! A quiet city, a peaceful refuge, beyond all human misery. How calm and isolated those misanthropes, those haters of humanity might live there, and all who have a distaste for social life!” “All! It would be too small for them,” replied Barbicane simply. CHAPTER XVIII. GRAVE QUESTIONS But the projectile had passed the _enceinte_ of Tycho, and Barbicane and his two companions watched with scrupulous attention the brilliant rays which the celebrated mountain shed so curiously over the horizon. What was this radiant glory? What geological phenomenon had designed these ardent beams? This question occupied Barbicane’s mind.