Tvrđa (Citadel) is the old town of the city of Osijek. It is the best-preserved and largest ensemble of Baroque buildings in Croatia and consists of a Habsburg star fort built on the right bank of the River Drava. Tvrđa has been described by the World Monuments Fund as 'a unique example of an eighteenth-century baroque military, administrative, and commercial urban center'.
The star fort was constructed in the immediate vicinity of medieval Osijek after the defeat of the Ottoman forces in 1687, due to Osijek's strategic importance. Constructed starting in 1712 to plans by Mathias von Kaiserfeld and then Maximilian Gosseau de Henef, all five planned bastions and two gates were complete by 1715. By 1735, the inner town was finished and three northern bastions had been added. When complete, it was the largest and most advanced Habsburg fortress on the border with the Ottoman Empire, consisting of eight bastions and featuring armories, depots, a garrison headquarters, military court, construction office, a garrison physician, guardhouse, officers' apartments, a military hospital and seven barracks. The completed fort was entirely surrounded with walls and palisades and had four main gates at each side. Tvrđa had street lights by 1717 and was the site of the first public water supply in Croatia, opened in 1751.
Tvrđa's military importance decreased after the Berlin Congress of 1878, with the increasing stability of the surrounding region. Most of the fort walls and fortifications were destroyed in the 1920s due to the obstacle they presented to the development of Osijek. While the fortifications have largely been removed, the fort's interior core remains intact and is now home to churches, museums, schools and other public buildings, as well as numerous bars and restaurants. Of the fortification system, only the northern side of the walls now remain intact, as well as parts of the first and eighth bastions along with the northern gate known as the 'water gate' (vodena vrata). Tvrđa sustained significant damage during the Croatian War of Independence during the 1990s and was featured on the 1996 World Monuments Watch List of Most Endangered Sites. It now features on Croatia's tentative list for consideration as a nominee for a World Heritage Site.References:
The Mosque–Cathedral of Córdoba, also known as the Great Mosque of Córdoba and the Mezquita is regarded as one of the most accomplished monuments of Moorish architecture.
According to a traditional account, a small Visigoth church, the Catholic Basilica of Saint Vincent of Lérins, originally stood on the site. In 784 Abd al-Rahman I ordered construction of the Great Mosque, which was considerably expanded by later Muslim rulers. The mosque underwent numerous subsequent changes: Abd al-Rahman II ordered a new minaret, while in 961 Al-Hakam II enlarged the building and enriched the Mihrab. The last of such reforms was carried out by Almanzor in 987. It was connected to the Caliph"s palace by a raised walkway, mosques within the palaces being the tradition for previous Islamic rulers – as well as Christian Kings who built their palaces adjacent to churches. The Mezquita reached its current dimensions in 987 with the completion of the outer naves and courtyard.
In 1236, Córdoba was conquered by King Ferdinand III of Castile, and the centre of the mosque was converted into a Catholic cathedral. Alfonso X oversaw the construction of the Villaviciosa Chapel and the Royal Chapel within the mosque. The kings who followed added further Christian features, such as King Henry II rebuilding the chapel in the 14th century. The minaret of the mosque was also converted to the bell tower of the cathedral. It was adorned with Santiago de Compostela"s captured cathedral bells. Following a windstorm in 1589, the former minaret was further reinforced by encasing it within a new structure.
The most significant alteration was the building of a Renaissance cathedral nave in the middle of the expansive structure. The insertion was constructed by permission of Charles V, king of Castile and Aragon. Artisans and architects continued to add to the existing structure until the late 18th century.
The building"s floor plan is seen to be parallel to some of the earliest mosques built from the very beginning of Islam. It had a rectangular prayer hall with aisles arranged perpendicular to the qibla, the direction towards which Muslims pray. The prayer hall was large and flat, with timber ceilings held up by arches of horseshoe-like appearance.
In planning the mosque, the architects incorporated a number of Roman columns with choice capitals. Some of the columns were already in the Gothic structure; others were sent from various regions of Iberia as presents from the governors of provinces. Ivory, jasper, porphyry, gold, silver, copper, and brass were used in the decorations. Marvellous mosaics and azulejos were designed. Later, the immense temple embodied all the styles of Morisco architecture into one composition.
The building is most notable for its arcaded hypostyle hall, with 856 columns of jasper, onyx, marble, granite and porphyry. These were made from pieces of the Roman temple that had occupied the site previously, as well as other Roman buildings, such as the Mérida amphitheatre. The double arches were an innovation, permitting higher ceilings than would otherwise be possible with relatively low columns. The double arches consist of a lower horseshoe arch and an upper semi-circular arch.