304 



CASA GRANDE RUIN. 



[ETH. ANN. 13 



flat surface as a base the structure rises to a height of 5 feet. From 

 the exterior it has the appearance of an ordinary mound, but on reach- 

 ing the top the interior is found to be hollowed out to a depth which 

 even at the present day is below the surrounding surface, although not 

 below the depressions adjoining. The main structure or mound is 

 shown in figure 329 (an enlargement from the map). It measures on 

 top of the crest 150 feet from north to south and about 80 feet from 

 east to west, but covers a ground area of 200 feet by 120 feet or over 

 half an acre. The crest is of the same height throughout, except for 

 slight elevations on the eastern and western sides and a little knoll or 





Contour InfervBl, I /oof 



uori 



FiQ. 329 Map of hollow mound. 



swell in the southwestern corner. There is no indication of any break 

 in the continuity of the crest such as would be found were there open- 

 ings or gateways to the interior. The bottom of the depression in the 

 main structure is at present about a foot below the surrounding ground 

 surface, but it must have been originally considerably more than this, 

 as the profile indicates long exposure to atmospheric erosion and conse. 

 quent filling of the interior. No excavation was made and the character 

 of the construction can not be determined, but the mound is apparently 

 a simple earth structure — not laid up in blocks, like the Casa Grande 



