When the Romans invaded Britain they
named the place Aquae Sulis,
building a huge complex around the springs, which they believed were a work of the gods.
The complex contained two roofed pools,
one for bathing (above),
and one other (where the hot springs rose) for worship, sacred to the gods.
The original roofs and ceilings have gone, and sunlight now
causes algae to give the pools' characteristic green colour.
Around the baths were built an enormous
array of temples, saunas, cold pools,
steam rooms, courtyards and altars for animal sacrifice.
The columns and balustrades above the
pool - complete with statues of Roman emperors -
are a later Georgian addition.