The Church of the Assumption of Our Lady, commonly known as the Rotunda of Mosta, is the third largest unsupported dome in the world and the third largest in Europe.
Built in the 19th century on the site of a previous church, it was designed by the Maltese architect Giorgio Grognet de Vassé. Its dome is among the largest in the world, with an internal diameter of 37.2 metres. the rotunda walls are 9.1 metres thick (necessary to support the weight of the dome). The rotunda dome is the third-largest church dome in Europe and the ninth largest in the world.
Grongnet's plans were based on the Pantheon in Rome. Construction began in May 1833 and was completed in the 1860s. The original church was left in place while the Rotunda was built around it, allowing the local people to have a place of worship while the new church was being built. The church was officially consecrated on the 15 of October 1871.
On April 9, 1942, during an World War II air-raid, a 500 kg Luftwaffe bomb pierced the dome and fell among a congregation of more than 300 people awaiting early evening mass. It did not explode. The same type of bomb as pierced the dome is now on display (the original was dumped at sea) at the back of the church in the Sacristy.
References:Saint-Georges de Boscherville Abbey is a former Benedictine abbey. It was founded in about 1113 by Guillaume de Tancarville on the site of an earlier establishment of secular canons and settled by monks from the Abbey of Saint-Evroul. The abbey church made of Caumont stone was erected from 1113 to 1140. The Norman builders aimed to have very well-lit naves and they did this by means of tall, large windows, initially made possible by a wooden ceiling, which prevented uplift, although this was replaced by a Gothic vault in the 13th century. The chapter room was built after the abbey church and dates from the last quarter of the 12th century.
The arrival of the Maurist monks in 1659, after the disasters of the Wars of Religion, helped to get the abbey back on a firmer spiritual, architectural and economic footing. They erected a large monastic building one wing of which fitted tightly around the chapter house (which was otherwise left as it was).