Located on Ludgate Hill, at the highest point of the City of London, St Paul’s Cathedral, which is one of the most famous and most recognizable sights of London, is also equally important, as it is the mother church of the Diocese of London and the seat of the Bishop of London. Its dome, framed by the spires of Wren's City churches, is among the highest in the world and has dominated the skyline for over 300 years.

The names of Saint Mellitus and Saint Erkenwald are very much associated with the establishment of the first St Paul’s Cathedral. Saint Mellitus, who arrived in Britain with Saint Augustine on a mission from Rome instigated by Pope Gregory the Great, founded St Paul’s in 604 AD. Saint Erkenwald was buried in the cathedral in 693 and the building, or a successor, was destroyed by fire in 962, but rebuilt in the same year. However, that was also burnt, with much of the city, in a fire in 1087.

The construction of the fourth St Paul's, generally referred to as the Old St Paul’s, began by the Normans after the 1087 fire, but a further fire in 1135 disrupted the work, and the new cathedral was consecrated in1240.By the 16th century the building started to decay and in1561, the spire was destroyed by lightning, which was claimed as a sign of divine retribution on England's Protestant rulers. Finally, the Old St Paul's was gutted in the Great Fire of London in1666 and discarding the idea of reconstruction, a decision was taken to build a new cathedral in a modern style.

The responsibility of designing the new building was entrusted to Sir Christopher Wren, a brilliant scientist and mathematician and Britain’s most famous architect. It took nine years to complete the design that would meet all the requirements of a working cathedral, including a Morning Chapel was required for Morning Prayer, vestries for the clergy to robe, a treasury for the church plate, a home for the enormous organ, bell towers, apart from the interior decoration, suitable for the grandest of occasions and ceremonies.

Construction commenced in 1675 and according to one contemporary account, the date of the laying of the first stone of the cathedral was 21 June 1675. However, according to another contemporary opinion, it was 25 June and according to the third on 28 June. Nevertheless, Sir Christopher Wren devoted thirty five years of his life to fulfill all the need and decorated the capital city with a wonderful building and provided a symbol for the Church of England. He lived to see the completion of the building, while the last stone of the Cathedral’s structure was laid on 26 October 1708 by his son, Christopher Wren Jr, along with Edward Strong, the son of the master mason. However, construction continued for several years after that, as the statues on the roof were added in the 1720s.

The final design of St Paul’s Cathedral was strongly rooted in St Peter’s Basilica in Rome, which differs substantially from the official design of Wren. Though it was built in a restrained Baroque style, it has strong medieval influences. It is quite evident that, much emphasis was given on its facade, which has been designed to define rather than conceal the form of the building behind it. The most prominent exterior feature of the building is the glorious dome, which rises 365 feet to the cross at its summit. It rises in two clearly defined stories of masonry, which, together with a lower unadorned footing, equal a height of about 95 feet.

Rather than the arrangement of alternating windows and projecting columns that Michelangelo had used in St Peter’s Basilica, Wren created a continuous colonnade around the huge drum of the dome. In addition, niches were placed between the columns in every fourth opening, to create diversity and the appearance of strength Above the colonnade rises the second stage surrounded by a banister balcony, decorated with alternating rectangular windows pilasters, set just below the cornice. The massive dome rises above this attic, covered with lead and ribbed in accordance with the spacing of the pilasters. The dome is raised on a tall drum above a gilded cornice and its painted decoration depicts eight scenes from the life of St Paul set in illusionistic architecture.

In each of its three bays, St Paul's has a 91 feet high nave and choir. The nave is separated from the aisles by an arcade of piers with attached Corinthian pilasters rising to an entablature. The domed narthex, consisting of the entrance or lobby area, located at the west end of the nave, is flanked by the Chapel of St Dunstan to the north and the Chapel of St George and the Order of St Michael to the south. The nave is 121 feet wide and across the transepts is 246 feet. Wide arches lead to the dome and the apse. The eastern apse, decorated with mosaics, extends the width of the choir and is the full height of the main arches across choir and nave.

The Crypt of St Paul’s extends the entire length of the building and houses over 200 monuments, which include the tombs of Admiral Lord Nelson, Arthur Wellesley Duke of Wellington, Alexander Fleming and Sir Christopher Wren, the architect of St Paul’s Cathedral.

During the Second World War, a time-delayed bomb had struck the Cathedral on 12 September 1940, which was successfully defused. However, during the Blitz, the German bombing campaign against the United Kingdom, it was struck by bombs on 10 October 1940 and 17 April 1941. While the first strike destroyed the high altar, the second strike on the north transept left a hole in the floor above the crypt. The present high altar made of marble, dates from 1958. It replaced a large Victorian marble altar and screen, which were damaged by the bombing.