Tre Kronor Museum is a museum about the old castle Tre Kronor, opened on December 28, 1999 in Stockholm Castle. The museum is located in the preserved cellars of the castle, in three crowns, in the oldest halls, dating back to the 1300s.
The museum is located in the basement vaults below the northern slope of the castle, with the entrance to the Lion's Mountain through a thick 13th century defensive wall. There are several models in the museum showing the appearance of the Stockholm Castle at various times from the defensive castle to the castle fire of 1697. Also on display are objects that were saved from the fire, such as the lower part of the marble columns with ornamented fittings. They were in the castle church of John III, which was then in the northern part of the castle, in the 157s.
From the museum lobby, a staircase leads down to the partially preserved underground corridor, which crossed a wooden bridge over the water to the courthouse in Helgeandsholmen. Charles XI built it so that he could discreetly pass from the castle into the stables.