The objective of this fortress construction was to provide defense at the entrance of Ciliwung .
The anchor points had been moved far away from the fortress due to the formation of shoals in front of the estuary and the widening of the coastline .
The objective of this fortress construction was to provide defense at the entrance of Ciliwung because the anchor points had been moved far away from the fortress due to the formation of shoals in front of the estuary and the widening of the coastline .