The dim traces of natural light grew stronger as they continued their journey through the galleried cave.
Suddenly, the eastern wall came to an abrupt end, opening out to display a huge ravine that stretched as far as the eye could see.
Waterfalls poured from fissures in the rockface whilst moss-covered walls danced with pin-points of golden light as thousands of tiny fireflies awoke to this unexpected intrusion.
The impression was that of gazing down upon a city at night dancing beneath the stars.