Within the larger enclosure are four elevated squares or truncated pyramids of earth, which, from their resemblance to similar erections in Mexico and Central America, merit a particular notice.[58] Three of these have graded passages or avenues of ascent to their tops. The principal one is marked A in the plan, and an engraving more clearly illustrating its features is herewith presented, Fig. 17. It is one hundred and eighty-eight feet long by one hundred and thirty-two wide, and ten high. Midway upon each of its sides are graded ascents, rendering easy the passage to its top. These grades are twenty-five feet wide and sixty feet long. The next in size is marked B in the plan, and is one hundred and fifty feet long by one hundred and twenty wide, and eight feet high. It has three graded passages to its top, viz. upon the north, west, and east. Those at the sides are placed somewhat to the north of the centre of the elevation. Upon the south side there is a recess or hollow way, instead of a glacis, fifty feet long by twenty wide. This elevation is placed upon an easy swell or ridge of land, and occupies the most conspicuous position within the enclosure, every part of which is commanded from its summit. A few feet distant from the northern glacis, is a small conical mound, surrounded with shallow excavations, from which the earth for its construction, and, perhaps, for the construction in part of the pyramidal structure, was taken. To the right of the elevation, and near the eastern angle of the enclosure, is a smaller elevation one hundred and twenty feet long, fifty broad, and six feet high. It had graded ascents at its ends, similar in all respects to those just described. It is now much obliterated. Near the northern angle of the work is another elevation, not distinctly marked. The two larger squares are covered with a close turf, and still preserve their symmetry. Indeed, no erections of earth alone could surpass them in regularity. They are perfectly level on the top, except where some uprooted tree has displaced the earth.
There is a passage or gateway one hundred and fifty feet wide, in the middle of the left wall of this enclosure, on the side next the Muskingum. Leading from it towards the river, and at right angles to the embankment, is the “«Sacra Via»,” a «graded» or «covered way» of singular construction. It is six hundred and eighty feet long by one hundred and fifty wide between the banks, and consists of an excavated passage descending regularly from the plain, upon which the works just described are situated, to the alluvions of the river. The earth, in part at least, is thrown outward upon either side, forming embankments from eight to ten feet in height. The centre of the excavated way is slightly raised and rounded, after the manner of the paved streets of modern cities. The cross section «g h» exhibits this feature. [p075] This section is constructed from measurements taken at a point midway between the top and base of the grade. Measured between the summits of the banks, the width of the way is two hundred and thirty feet. At the base of the grade, the walls upon the interior are twenty feet high. From this point there is a slight descent, for the distance of several hundred feet, to the bank of the river, which is here thirty-five or forty feet in height. It has been conjectured by some, that the river flowed immediately at the foot of this way at the time of its construction. This is, however, mere conjecture, unsupported by evidence. If admitted, it would give to this monument an antiquity greatly superior to that of the pyramids, unless the deepening of our river channels has been infinitely more rapid in times past, than at present. But one fact favors the conjecture, and that is the entire absence of remains of antiquity upon the beautiful terraces to which this graded passage leads. They may nevertheless have been once as thickly populated as they now are; and this passage may have been the grand avenue leading to the sacred plain above, through which assemblies and processions passed, in the solemn observances of a mysterious worship.