Medininkai Castle was built in the late 13th or early 14th centuries. According to the space covered, it is the largest castle in the present territory of Lithuania. The castle was built in the transitional period from the Romanesque to the Gothic style, and it is one of the earliest enclosure castles in Lithuania. In the Grand Duchy of Lithuania (GDL), the old Kaunas Castle (destroyed in 1362), Krėva Castle, and Lida Castle were of the same type as Medininkai Castle. The latter two are now in the territory of present Belarus.
Medininkai Castle is situated 32 km from the centre of Vilnius. The castle was built on a plain, surrounded by a swamp from the North and from the West; in the middle of the swamp, ran a nameless brook. The plan of the castle has survived till the present day without essential changes. A square courtyard covers the space of 1,85 hectares; together with two wide fossae and two ramparts its space is 6,5 hectares. The upper part of the defensive wall did not survive; the wall was from 14 to 15 metres in height and had approximately 280 arrow loops. The length of the wall totalled 563 metres. There were 4 entrance gates in the wall: the upper gates, installed in the northern and southern walls, were 5 metres above the ground; the lower gates were in the eastern and western walls. The castle had 4 towers. The most important of them was the five-storey keep (donjon), situated in the northern corner; originally it was 30 metres in height, however, only 23 metres of it survived in the course of time. The ceilings of the first four storeys were wooden, meanwhile, the top floor had a brick-built ogival arches. The keep served for defence, but also was used as living space.
The castle was for the first time mentioned as a military object in 1402, when the Grand Commander of the Teutonic Order, Wilhelm von Helfenstein, did not manage to capture Vilnius, but seized and burned down Medininkai Castle; apparently only the wooden buildings were destroyed by fire, as historical sources of the late 14th and early 15th centuries describe Medininkai Castle as stone construction. Medininkai Castle played the most important role in the late 14th and early 15th centuries. It is known that Vytautas the Great wrote 2 letters at this Castle. In the second half of the 15th century, Medininkai Castle was mentioned in the Lithuanian Metrica: the Grand Duke granted several peasants to the nobles in this county. In the beginning of the 16th century, the wooden buildings in the courtyard suffered from fire, and a wooden manor was erected there some decades later. After the manor ruined, the territory was used as a kitchen garden. The abandoned castle suffered from wars in 1655 and 1812. The ruins of the castle were included into the ‘Map of Castles’ of Vilnius Governorate in 1827, and depicted in the painting by N. Orda in the middle of the 19th century.
The ruins of Medininkai Castle attracted the attention of the restorers in 1954: the measurements were taken, a geodetic photo was made, and both the restoration and preservation projects were prepared. The restoration works began in 1959; many prominent architects, such as S. Lasavickas, E. Purlys, J.Glemža, took part in this work. The project was suspended in 1981, and the restoration was renewed only ten years later, under the project offered by the architect S. Mikulionis. After the death of the architect S. Mikulionis, his work was continued by the architects M. Mikulionytė and J. Glemža, who won the project for the restoration of the keep of the castle. On January 17th 1992, a restoration fund of Medininkai Castle was established. The symbolical first stone was laid in the restored keep on the 6th of July 1993, on the day of the 740th anniversary of King Mindaugas Coronation. A permanent exhibition of Trakai History Museum opened in the keep of Medininkai Castle in 2012; various festivals and events take place in the courtyard of the ancient castle since then.