It is now a museum.
A fortress was built at the location in the 1370s by Bo Jonsson Grip.
It was sold to queen Margaret in 1404, and remained the property of the crown until it was acquired by Sten Sture the Elder in 1472.
It was donated to a convent for males of the order of the Carthusians in 1498, and functioned as a convent for almost thirty years.
The King tore it down, and built a fortified castle with circular corner towers and a wall, for defensive purposes.
Of the original medieval fortress, only the façade of a wall remains.