The caves in which the purification baths were found were 'caves of refuge,' where Jews who lived in the area sought shelter under Roman rule.

By Eli AshkenaziThe caves in which the purification baths were found were "caves of refuge," where Jews who lived in the area sought shelter under Roman rule, particularly during the Jewish revolt that ended with the destruction of the Second Temple.
According to Shivtiel, the effort needed to build mikvehs under such difficult circumstances indicates that these cave dwellers were probably kohanim.
"These people saw it as an imperative to build a mikveh in their shelter, in a cave on a steep cliff," he said.
Shivtiel and Vladimir Boslov of the Hebrew University's cave research unit have already discovered 500 caves of refuge during the comprehensive survey they've been conducting under the auspices of the Israel Nature and Parks Authority.
To reach this particular cave, the two researchers had to scale a cliff "with our fingernails," as Shivtiel put it.
"The preparation of mikvaot in these refuge caves, sites that are difficult to access and are not meant for routine living but for times of distress, teach us the deep religious need for facilities for ritual purity," said Shivtiel. "The preparation of mikvehs in these places is not amazing just because of the physical difficulty in digging them, but because in doing so one needs to cope with all the specifics of Jewish law that a mikveh demands, primarily a source of flowing water and an immersion area that has a specific volume."
The mikveh builders at Arbel assured supplies of natural water by either building the ritual baths directly under still-dripping stalactites or by digging tunnels from the mikvehs to outside the rock wall, so that runoff from rainwater could accumulate.
Three of the mikvehs on the cliffs were documented by archaeologist Ronny Reich of Hebrew University, but Shivtiel and Boslov discovered two more.
Other findings that they and others have uncovered in the Arbel region show that these cave dwellers lived at subsistance level and in crowded conditions. They had water, food and light, as evidenced by the water-storage pits, niches for candles, and remnants of cooking pots and pitchers, but no more than that.
Shivtiel, who consulted with rabbis to identify the mikvehs, said they were distinguished from other water cisterns by three things: steps heading into the bath, a water supply from a natural source and enough water to immerse one's entire body.
"Preparing a mikveh is beyond what is needed to sustain life," Shivtiel said. "The Jewish group most likely to see it as an integral part of their lives would be a group that was part of the mishmarot kehuna [priests who did shifts at the Temple]."
Previous research has shown that when the priests found refuge in the Galilee after the destruction of the Second Temple, at least one group moved to Arbel.


http://www.haaretz.com/news/national/israeli-researcher-mikvehs-show-that-galilee-cave-dwellers-were-likely-kohanim-1.426773