It looks to me like a scene out of the second Matrix movie, but it is a summer solstice gathering in Zugarramurdi, Spain,
to commemorate the burning of "witches" in the Spanish Inquisition. "a commemoration to the witches "that used the cave," many of whom were burnt alive during the Basque witch trials." According to Environmental News,
"The cave has no electric illumination system and light comes from blazing torches and fires. The summer solstice has a mystical and religious significance to some people and for many it is a simple motive for celebration."
::Environmental News picture credit National Geographic