 On the following day , elements of the U.S. 1st Air Cavalry division entered what came to be known as " The City " , southwest of <unk> . The two @-@ square mile PAVN complex contained over 400 <unk> <unk> , storage sheds , and bunkers , each of which was packed with food , weapons , and ammunition . There were truck repair facilities , hospitals , a lumber yard , 18 mess halls , a pig farm , and even a swimming pool . Forty kilometers to the northeast , other 1st Cavalry Division elements discovered a larger base on 6 May . Nicknamed " Rock Island East " after the U.S. Army 's Rock Island Arsenal in Illinois , the area contained more than 6 @.@ 5 million rounds of anti @-@ aircraft ammunition , 500 @,@ 000 rifle rounds , thousands of rockets , several General Motors trucks , and large quantities of communications equipment . 
