It is oval shaped , 189 meters ( 615 ft \/ 640 Roman feet ) long , and 156 meters ( 510 ft \/ 528 Roman feet ) wide . It covers an area of 6 a. The outer wall is 48 meters ( 157 ft \/ 165 Roman feet ) high . It is elliptical in plan and is 189 meters ( 615 ft \/ 640 Roman feet ) long , and 156 meters ( 510 ft \/ 528 Roman feet ) wide , with a base area of 6 a. The height of the outer wall is 48 meters ( 157 ft \/ 165 Roman feet ) .