Biržai Castle is an earth bastion-type castle. The construction started in 1586 by the order of Krzysztof Mikołaj Radziwiłł. In 1575, preparing for this construction, a dam was built on the Agluona and Apaščia rivers at their confluence, and the artificial Lake Širvėna, covering about 40 km², was created. Major castle building works were finished in 1589.
Since the second half of the 17th century, the castle has been the main seat of the Biržai-Dubingiai Radziwiłł family line, which was transferred here from the Dubingiai Castle. Biržai Castle served as a major defensive structure during the wars with Sweden.
The castle was reconstructed from ruins in the 1980s, in the Renaissance-Baroque style. The residential manor of the castle houses a library and a regional history museum 'Sėla' (literally Selonia), founded in 1928.
References:The trulli, typical limestone dwellings of Alberobello in the southern Italian region of Puglia, are remarkable examples of corbelled dry-stone construction, a prehistoric building technique still in use in this region. These structures, dating from as early as the mid-14th century, characteristically feature pyramidal, domed, or conical roofs built up of corbelled limestone slabs. Although rural trulli can be found all along the Itria Valley, their highest concentration and best preserved examples of this architectural form are in the town of Alberobello, where there are over 1500 structures in the quarters of Rione Monti and Aja Piccola.
The property comprises six land parcels extending over an area of 11 hectares. The land parcels comprise two districts of the city (quarters or Rione Monti with 1,030 trulli; Rione Aia Piccola with 590 trulli) and four specific locations.
Trulli (singular, trullo) are traditional dry stone huts with a corbelled roof.