prohodna cave`s eyes of god b&w

115ft 148ft 262m 35m 45m 860ft adrenaline and attraction big black bulgaria cave ceiling climber climbers cold contrast daylight entrance entrances eye eyes god gorge graphical height high holes iskar karlukovo karst like long longest lovech lukovit municipality nature oknata opposite passage phenomenon popular prohodna province pure rock rope season small summer tourist travel two village white