Archaeological research in the area of Ljubljana Castle has been ongoing since the 1960s. It was then that the first investigations were made as part of conservation interventions. In 1988, archaeologists from the City Museum of Ljubljana, in cooperation with conservators from the Ljubljana District Unit of the Institute for the Protection of Cultural Heritage of Slovenia, started to carry out more extensive and systematic preventive excavations in connection with the castle's planned renovation. These investigations revealed traces of settlement on the Castle Hill from prehistory through to the modern era.

Castle Hill had already been inhabited prior to the castle itself being built. This is shown by modest prehistoric remains discovered during previous investigations. The excavations this year include new finds dating from antiquity, including a 4th-century coin and the remains of a Roman blacksmith's forge.

Past research has also revealed traces of the earliest wooden fortifications from the 11th and 12th centuries, which stood in this area even before the construction of the stone medieval fortress in the 12th century and the town square walls, built no later than the early 13th century, which connected the castle and the town into a single defensive complex. Among the more significant discoveries from this period, uncovered during recent excavations, are the remains of a palisade structure, a potter’s kiln, and an old access road that connected the castle to the town. 

In the 15th century, the threat of Turkish incursions prompted extensive fortification of the castle. Emperor Frederick III ordered a renovation of the defensive system, and the castle took on the appearance that we still recognize in its basic features today. At that time, a new access road was also established, leading from the entrance tower toward the main entrance to the castle building, the casemate tower. During this period, the city walls were also completely rebuilt. Of particular significance are the recent discoveries of the former entrance tower, the defensive moat, and the medieval path across the bastion, which shed light on the development of the defensive system of Ljubljana Castle and the city. 

Among the most significant finds are the remains of a masonry gate on the western side of the castle hill, the exact location of which had remained unknown to researchers for decades. This discovery significantly enhances our understanding of the connection between the castle and medieval Ljubljana, as well as the evolution of access to the castle over time.