Hammersta castle was a 13x18m wide two-storey stone building built around the year 1300 by Eringilse Nilsson, who's father was married to a sister of Bridget of Sweden. Eringilse's son (with the same name), was married to a Danish woman, Brita Olofsdotter Tott, and when the situation between Sweden and Denmark became tense around 1450, Tott was sentenced to death for spying for the Danes. Luckily for Brita she was pardoned and later paid for the famous fresco paintings that you can now see at the Ösmo Church.
The castle was abandoned in the 15th century. Between 1628 and 1767 the estate was owned by Horn, Kruus and Wrede families. The new manor house building was started in 1685 and completed in 1723.
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.