The narrows at Drøbak, called Drøbaksundet, is a natural point for the naval defence of Oslo, the capital of Norway. The first defences were constructed during the reign of Christian IV of Denmark and Norway and were ready in 1644. The fortifications were however not involved in battle during the Hannibal War. After the war the fortifications were dismantled, and only resurrected for a short period during the 1814 war with Sweden.
Around 1830 the discussion started for a renewed fortification of the Drøbak Narrows and the first stage was ready in 1848, the next in 1853. The name of the fortress was given by royal resolution on 23 August 1855 after a visit by the Swedish-Norwegian King Oscar I.
By the end of the 19th century the art of war developed rapidly and the new fortress was soon obsolete. The tension was also growing between the two countries in the union and so the Norwegians decided to upgrade the fortress. From 1890 new improved German guns were installed, an underwater barrier was built in 1874–79, and an underwater torpedo battery was constructed. The main armament was three 28 cm calibre guns manufactured by Krupp. There were also a number of guns with smaller calibres on the mainland. An underwater barrier went from the main islet of Kaholmen and south-west to Hurum on the western side of the fjord, thus making it impossible for large vessels to sail west of the fortress.
Having been constructed in 1898–1901, and taken into service on 15 July 1901, the underground torpedo facility remained one of the few Norwegian defence installations unknown to German military intelligence at the point of the 1940 invasion. The battery was one of two in Norway and it was designed to launch its torpedoes from under the water level. At Oscarsborg the torpedo battery is a concrete construction inside a cave mined into the rock of the North Kaholmen island.
When Norway was invaded on 9 April 1940, all of the fortress' armament was over 40 years old, and of German origin. Both the guns and the torpedo battery worked flawlessly when Oscarsborg encountered one of the German invasion flotillas; they sank the heavy cruiser Blücher, and threw back the German naval force heading for Oslo, thus managing to save the Norwegian King and government from being taken prisoner. The fortress was returned to Norwegian control on 12 May 1945 when Captain Thorleif Unneberg took command of the fortifications and raised the Norwegian flag following the capitulation of all German forces in Norway four days earlier.
During the Cold War Oscarsborg formed a last line of defence for the capital city, with the underground torpedo battery remaining secretly active up until 1 January 1993, having been modernized in the 1980s. After the deactivation of the last weapons systems, the remaining military activity on Oscarsborg consisted of the Coastal Artillery officer training programme. The officer school was officially shut down in 2002. The fortress is now largely a civilian resort and attraction, open for visitors. The scenic surroundings is much used for conferences and excursions. Visitors take a short motor launch trip from Drøbak.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.