One of the most complete surviving friaries of Dominican 'black friars' in England
Due to its good geographical positioning, Gloucester was as important as London and Winchester in Norman times.
When the Normans arrived they realised the strategic importance of the city.
The first thing they did was to build a large castle in the South West corner of the town sitting on the banks of the River Severn.
Here they were able to control this part of the country and the lands on the other side of the river into Wales.
Although the castle can no longer be seen, elsewhere the Normans left a lasting mark on the city.
"Their influence in Gloucester was very strong," said Phil Moss from English Heritage.
"You find from that time onwards a lot of the city's growth was really influenced by a certain amount of Norman construction that was carried out here."
One of the best remaining examples is Blackfriars Priory in Gloucester, constructed in the early 13th Century.
There you will find the oldest surviving purpose built library in Great Britain.
Phil Moss said: "Henry III, who was crowned in Gloucester, was a great patron.
The original timbers in the 'scissor-braced roof' came from the Forest
"He gave money for the fabric of the building, he gave oaks from the Royal Forest [of Dean] for the roof and it is believed he gave the land upon which the Priory still stands."
So what influence did the Friars have in the county?
"The first friars that came here to Gloucester were the Greyfriars - the Franciscans - who arrived in 1231", added Phil Moss.
"The Blackfriars were the order of preachers, the great Friars preachers, and they established the Priory which was really a major regional school.
"The idea was that the Friars would be educated within the Friary and then they would go out into the county, wandering around visiting all the various parishes and parish churches.
"I think their influence within the county would have been very strong indeed."