Trakai Island Castle – buildings that breathe simplicity and modest elegance – embodied the most advanced 15th-century ideas of fortification (defensive engineering). It is regarded as a masterpiece of medieval defensive architecture and the only water castle in Eastern Europe. All the dukes of the Grand Duchy of Lithuania lived in Trakai Island Castle. Only Sigismund Augustus broke this tradition when he had a palace built in Vilnius, at the foot of Gediminas Hill. Large-scale research on the castle grounds began in 1951, and in 1962 the Trakai History Museum opened in the restored palace. In addition to the museum's permanent exhibition, the castle courtyards and halls host various exhibitions, conferences, music festivals and performances. Ancient Crafts Days, Vytautas the Great historical evenings and other events in the castle courtyard have become a tradition. Educational programmes for children and adults are also on offer. Just as in the old days, official foreign delegations visit Trakai Island Castle, and kings, presidents, ministers and ambassadors are received here. Since 1962 the Trakai History Museum has occupied the central palace of Trakai Island Castle, giving visitors the chance to walk around the ancient castle and see its austere interior and a wealth of interesting exhibits. Visitors learn about the history of the town of Trakai, its castles and the unique Trakai land. A further 16 exhibition halls are located in another part of the fortress, the so-called casemates – fortifications that protected against artillery shells. In the casemate halls you can see extensive collections of applied art: pipes, clocks, furniture, porcelain, glass and bone ware. There are also plenty of coins, medals, old maps, hunting trophies, jewellery, household items, knights' armour and weapons, and valuable paintings. In total, the museum's collections number almost 400,000 items! It is worth mentioning that in 2005 an exhibition of sacred art opened to visitors in the Dominican chapel on the grounds of the other castle – Trakai Peninsula Castle.