Sunpu Castle was enormous. Only the inner ring remains today. This former third citadel measures 44.5 acres. The grounds constituting today’s park is flat and open accented with sculpted gardens and lined with ancient trenches. During the 17th century, this was a twisting maze of high walls where defenders could shower attackers with arrows, rocks, guns, bamboo spikes and hot liquids. In the center was a courtyard called a baily or hon maru. This is where a fortified tower (keep) stood as the final line of defense.