Kalmar Castle is located about 300 kilometers southwest of Stockholm, on the shores of the Baltic Sea. The first building erected in the 12th century in the castle complex was a circular tower that served as a defense. At the end of the 13th century, a fortress was built which contained a wall surrounding the original tower and contained circular towers at its corners and square towers at the gates of the walls. From 1856 to 1941, several architects took turns in the extensive restoration project of this castle, starting from the fortress itself, to making detailed plans and rebuilding the moat, drawbridge and earthworks. The famous alliance was signed in this fortress in 1397, where the crowns of Denmark, Norway, and Sweden were united, to which the territory of today's Finland also belonged at that time. Today, this is one of the best-preserved medieval fortresses in Sweden.