"The Cathedral Church of the Holy and Undivided Trinity is the Church of England cathedral in the city of Bristol, England, and is commonly known as Bristol Cathedral. Founded in 1140, it became the seat of the bishop and cathedral of the new Diocese of Bristol in 1542.
Located on College Green, across which its architecture can be seen to advantage, the cathedral presents a harmonious view of tall Gothic windows and pinnacled skyline that belies the fact that it was constructed over a period of more than 700 years.
The cathedral has much of interest including unique architectural features, unusual memorials and a historic organ. 
Bristol Cathedral was founded as St Augustine's Abbey in 1140 by Robert Fitzharding, a wealthy local landowner and royal official. As the name suggests, the monastic precinct housed Augustinian canons. The original abbey church, of which only fragments remain, was constructed between 1140 and 1148 in the Romanesque style, known in England as Norman. Further stone buildings were erected on the site between 1148 and 1164. Three fine examples of this phase survive, the chapterhouse and the abbey gatehouse, now the diocesan office, together with a second Romanesque gateway, which originally led into the abbot's quarters. T.H.B. Burrough describes the former as the finest Norman chapter house still standing today.
Under Abbot David (1216–1234) there was a new phase of building, notably the construction in around 1220 of a chapel dedicated to the Blessed Virgin Mary, abutting the northern side of the choir. This building, which still stands, was to become know as the "Elder Lady Chapel". The architect, referred to in a letter as 'L', is thought to have been Adam Lock, master mason of Wells Cathedral. The stonework of the eastern window of this chapel is by William the Geometer, of about 1280.
Under Abbot Edward Knowle, a major rebuilding of the Abbey church began. Between 1298 and 1332 the eastern part of the abbey church was rebuilt in the English Decorated Gothic style.
Rebuilding appears to have ceased for about a hundred years, then, in the mid 15th century, the transept and central tower were constructed.
Abbot John Newland, (1481–1515), began the rebuilding of the nave, but it was incomplete at the Dissolution of the Monasteries in 1539. The partly built nave was demolished and the remaining eastern part of the church closed until it reopened as a cathedral under the secular clergy. In an edict dated June 1542, Henry VIII and Thomas Cranmer raised the building to rank of cathedral of a new Diocese of Bristol. The new diocese was carved out of the neighbouring dioceses and Paul Bush, (d. 1558) a former royal household chaplain, was created the first Bishop of Bristol. The new cathedral was dedicated to the Holy and Undivided Trinity,
With the 19th century's Gothic Revival signalling renewed interest in Britain's ancient architectural heritage, a new nave, harmonious in style with the eastern end, was added between 1868 and 1877 by George Edmund Street. The opening ceremony was on 23 October 1877. However the west front with its twin towers, designed by John Loughborough Pearson, was only completed in 1888." - Wikipedia