In 1884, the construction of the heir to the throne's castle was completed, in the cornerstone of which a poem by Prince Nikola was engraved. The building, called "Blue Castle" in recent times, represents one of the most beautiful buildings in the urban fabric of Cetinje. The architect of this lovely late Empire style building is unknown.
The construction of the heir to the throne's castle was of great importance for Cetinje, because after the start of the works, the Montenegrin lord declared that Cetinje would remain the permanent capital of Montenegro, after which the city rapidly developed and expanded territorially. In the interwar period and during World War II, this elegant building with pilasters made of red terrazzo stone with golden capitals housed the Great Gymnasium. Today, the Castle functions as an exhibition gallery.