San Nicolás church dates back to medieval times, although it has been much altered over the centuries. It is named in the Law of Madrid of 1202 as one of the oldest parishes in the city. Today it is the oldest church in Madrid, after the demolition of the Church of Santa Maria de la Almudena. Archaeological remains suggest that the church and its bell-tower may have been part of a former mosque. It was likely constructed during the 12th century. The nave and chapels were renovated in the 17th century.
By the 19th century, this church was poor in resources and parishioners. The parish was joined to that of El Salvador in 1805. For a time, the building was abandoned till the church was ceded in 1825 to the Third Order of Servites. When the nearby church of El Salvador was destroyed in 1842, this church gained its former status as a parish church.
In the year 1891 the parish was relocated to a church that had been Anton Martin Hospital in Atocha street, today the Parish of San Nicolas and San Salvador, leaving the old building as the church of 'St. Nicholas of the Servites', a name derived from the Servite Order, which still owns it.
At the end of century profile interventions have been implemented, the main one being held in 1983. In some of these interventions was the replacement of the stone, he must be very poor, in the apse, where they appreciate different finishes to the original stone.
The most interesting feature of this temple is undoubtedly its tower, dating from the 12th century except the Herrerian style spire tops, made of slate for the 18th century. It has a square and is constructed of brick decorated with blind arches. The brick has dimensions of 30 x 15 cm in the lower parts, but it was the brick bell tower area are smaller and of a different hue. This tower possibly corresponds to one of the Arab minarets preserved in the city. The tower was transformed in the 14th century, when it changed the cover, which was subsequently replaced by the spire.
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The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.