Archaeologists have uncovered the remains of what they believe could be a Bronze Age bathing site, or a sauna.
The metre-deep pit with a channel to a nearby stream was discovered at Stronechrubie, Assynt, in the north west Highlands.
The find was made by the Fire and Water Project, which is run by archaeology and history group Historic Assynt.
The project team had been trying to understand what a crescent shaped mound of stones had been created for.
Excavations at the mound by archaeologists and volunteers unearthed the pit and channel from beneath a layer of clay.
Archaeologists believe it may have been created for bathing, or as a sauna.
They said other possible uses for the site included cooking and feasting, or perhaps brewing.
Gordon Sleight, projects leader for Historic Assynt, said: "Under a strange layer of clay, we came down to a 1.5 metre square, one metre deep pit dug into the ground with a channel to feed water in from a nearby burn, plus three slabs which may indicate it was once lined with stone.
"There were no animal bones or anything to suggest its use as a cooking site and its size would have made it well-nigh impossible to bring to boiling point.
"So warm water is more likely, which suggests it was used for bathing, or perhaps as a sauna or sweat lodge."
Assynt is peppered with ancient sites, including the ruins of a 2,000-year-old home called a broch
Historic Assynt believe Clachtoll broch was built and occupied by a sophisticated maritime culture stretching up to the Northern Isles and out to the Hebrides at a time before the Roman conquest of southern Britain.
The tower may have been seen by ancient Greek geographer Pytheas during his circumnavigation of Britain.