The square keep, known as the Great Tower, was constructed in the mid-12th century from Bargate stone. Originally built with only two floors, it was a "solar keep" and functioned primarily as a private residence, rather than as an administrative centre. At an unknown later date, a third storey was built directly on top of the crenelations, to bring the structure to its present height. Part of the keep was in use as a prison by the end of the 12th century and new, royal apartments were constructed in the 13th century in the southwestern corner. Henry III commissioned the rebuilding of the castle following a fire in the mid-13th century, converting it into one of the most luxurious palaces in England. In 1245, he bought land to extend the castle grounds and Castle Arch was constructed on his orders in 1256.
The square keep, known as the Great Tower was constructed in the mid-12th century from Bargate stone. Originally built with only two floors it was a "solar keep" and functioned primarily as a private residence, rather than as an administrative centre. At an unknown later date, a third storey was built directly on top of the crenelations, to bring the structure to its present height. Part of the keep was in use as a prison by the end of the 12th century and new, royal apartments were constructed in the 13th century in the southwestern corner. Henry III commissioned the rebuilding of the castle following a fire in the mid-13th century converting it into one of the most luxurious palaces in England. In 1245, he bought land to extend the castle grounds and Castle Arch was constructed on his orders in 1256.