Originally there was a chapel situated on the site of the current Aa-kerk church. This chapel was devoted to Mary and to Saint Nicholas, the patron of the bargees who cast off the vessels at the Westerhaven.
In 1247, the chapel became the parish church and was named Onze Lieve Vrouwe ter Aa (Our Lady at the Aa) - Aa being the nearby river. Groningen had two centers at the time. One of them was around the chapel. Here lived the fishermen and the traders. Between 1425 and 1465, the chapel was changed into a brick church with a transept.
Images of the Siege of Groningen in 1672 show Der Aa-kerk without the top of the tower. After the war a new wooden tower top was built. On 23 April 1710, the tower spontaneously collapsed killing two people. In 1711, a new tower was built.
References:The Walls of Constantinople are a series of defensive stone walls that have surrounded and protected the city of Constantinople (today Istanbul) since its founding as the new capital of the Roman Empire by Constantine the Great. With numerous additions and modifications during their history, they were the last great fortification system of antiquity, and one of the most complex and elaborate systems ever built. They were also the largest and strongest fortification in both the ancient and medieval world.
Initially built by Constantine the Great, the walls surrounded the new city on all sides, protecting it against attack from both sea and land. As the city grew, the famous double line of the Theodosian Walls was built in the 5th century. Although the other sections of the walls were less elaborate, they were, when well-manned, almost impregnable for any medieval besieger.