Since no one traveled except by order of the Inca, the highways were reserved for himself, the armies, and the _chasqui_, or royal runners. From Zarate to Humboldt, they have been described as fit to rank with the seven wonders of the world. One highway pierced walls of solid rock, crossing profound chasms and the treacherous marshes of the _puna_ on walls of solid masonry. Being a pedestrian road, it slipped in flights of stone steps over the brow of the mountains. It traversed the whole empire for two thousand miles among the mountain-tops. The other, flanked by mud walls, lay along the low deserts of the coast, “shaded by trees whose branches hung over the road loaded with fruit, and filled with parrots and other birds,” to quote Cieza de Leon. Humboldt said that “part of the coast road was macadamized.” At regular intervals, “every ten thousand paces,” _tambos_ were scattered along the roads, houses of pleasure for the Inca and waiting-houses for the relays of messengers of the Sun as they bore news of royal necessity, or brought fish from the sea or other delicacies from distant provinces to the Inca’s table. Garcilasso describes the stone stairs up to these inns “where the chairmen who carried the sedans did usually rest, where the Incas did sit for some time taking the air, and surveying in a most pleasant prospect all the high and lower parts of the mountains, which wore their coverings of snow, or on which the snow was falling, for from the tops of some mountains one might see a hundred leagues round.” The Incas threw a swinging osier-bridge of spider-web construction across a vicious torrent to lead their armies over. So-called historians tell of bridges of feathers used in Inca days, but, as Garcilasso adds, “omit to declare the manner and fashion of them!” The secrets of the Inca ruins are not yet told. For their industry moulded underground as well, connecting palaces and convents by hidden passageways, and chambers and depositories for army supplies like those made by the great Yupanqui in his campaign against the Chimus. The subterranean system of water-works was stupendous. Near Cajamarca is a channel several hundred miles long paved with flagstones throughout its entire length. It forms the outlet to a little lake. Another aqueduct traversed the whole province of Cuntisuyu, twelve feet deep and over one hundred and twenty leagues long, leading waters of the snows to barren plains. Water was stored in cisterns on the mountain-tops. “They conducted rivers in straightened channels through hills of solid rock,” they brought water through pipes of gold from distant hot and cold springs, whose sources are now unknown. It trickled into the baths of the Inca through golden jaws of animals, birds, or snakes, and then welled [Illustration: Copyright by Underwood & Underwood, N. Y. AN HEIR OF THE “MAKERS OF RUINS.”] over through properly regulated pathways to the terraces, where growing things were in want of irrigation.