Feature 81 is another large, rectangular basin with a smaller basin projecting to the west. It is located in the northeastern quadrant of the Miami Circle, near the northern edge of the arc of large basins. The walls of both basins are nearly vertical and bear obvious tool marks. Eight smaller holes occur in the bottom of the basins, primarily clustered in an arc along the southern side of the feature. The excavation notes show a large number of limestone cobbles piled in the bottom of the feature.