The baths have been modified on several occasions, including the 12th century, when John of Tours built a curative bath over the King's Spring reservoir, and the 16th century, when the city corporation built a new bath (Queen's Bath) to the south of the spring.
The spring is now housed in 18th-century buildings, designed by architects John Wood, the Elder and John Wood, the Younger, father and son.
Visitors drank the waters in the Grand Pump Room, a neo-classical salon which remains in use, both for taking the waters and for social functions.
Victorian expansion of the baths complex followed the neo-classical tradition established by the Woods.
In 1810 the hot springs failed and William Smith opened up the Hot Bath Spring to the bottom, where he found that the spring had not failed but had flowed into a new channel.
Smith restored the water to its original course.

The visitor entrance is via an 1897 concert hall by J. M. Brydon.
It is an eastward continuation of the Grand Pump Room, with a glass-domed centre and single-storey radiused corner.
The Grand Pump Room was begun in 1789 by Thomas Baldwin.
He resigned in 1791 and John Palmer continued the scheme through to completion in 1799.
The elevation on to Abbey Church Yard has a centre piece of four engaged Corinthian columns with entablatures and pediment.
It has been designated by Historic England as a grade I listed building.
The north colonnade was also designed by Thomas Baldwin.
The south colonnade is similar but had an upper floor added in the late 19th century.
The museum and Queen's Bath including the "Bridge" spanning York Street to the City Laundry were by Charles Edward Davis in 1889.
It comprises a southward extension to the Grand Pump Room, within which some parts of the 17th-century Queen's Bath remain.
The baths have been modified on several occasions, including the 12th century, when John of Tours built a curative bath over the King's Spring reservoir, and the 16th century, when the city corporation built a new bath (Queen's Bath) to the south of the spring. The spring is now housed in 18th-century buildings, designed by architects John Wood, the Elder and John Wood, the Younger, father and son. Visitors drank the waters in the Grand Pump Room, a neo-classical salon which remains in use, both for taking the waters and for social functions. Victorian expansion of the baths complex followed the neo-classical tradition established by the Woods. In 1810 the hot springs failed and William Smith opened up the Hot Bath Spring to the bottom, where he found that the spring had not failed but had flowed into a new channel. Smith restored the water to its original course.
The visitor entrance is via an 1897 concert hall by J. M. Brydon. It is an eastward continuation of the Grand Pump Room, with a glass-domed centre and single-storey radiused corner. The Grand Pump Room was begun in 1789 by Thomas Baldwin. He resigned in 1791 and John Palmer continued the scheme through to completion in 1799. The elevation on to Abbey Church Yard has a centre piece of four engaged Corinthian columns with entablatures and pediment. It has been designated by Historic England as a grade I listed building. The north colonnade was also designed by Thomas Baldwin. The south colonnade is similar but had an upper floor added in the late 19th century. The museum and Queen's Bath including the "Bridge" spanning York Street to the City Laundry were by Charles Edward Davis in 1889. It comprises a southward extension to the Grand Pump Room, within which some parts of the 17th-century Queen's Bath remain.
Roman Baths (Bath)