But the cavity was clearly not a natural cave or a river-cut grotto.
Its gardens, designed by William Kent, are fantastic: beds of foxgloves and poppies, big river, crested newts, grottoes, longhorn cattle and a 17th-century dovecote like a Parthenon high rise.
Celebration settings are impressive -- from the Wailua River region whose hau trees have heart-shaped leaves to up-river where the Fern Grotto is a ecological wonder, drippy and covered with exotic plants.
It's not corralled into parks or gardens, but just lies there, free, under the heavens - and if you ramble about its tracks, lanes and roads, you'll bump into any number of folk ready to point you on to the waterfalls, grottos, rivers or lakes.
Naher el Kalb is the name of the river that runs through the grottoes, while Jeita, meaning "roaring water" in Aramaic, is the town in which the cave's entrance is located.
The main attraction is a boat journey along the underground river that takes the visitor to Glowworm Grotto, lit by countless glowworms.
"I haven't had my say yet," he said, staring out over the garden toward the grotto, on the hill beyond the river, as a fountain splashed and birds called to one another in the trees.
Uninvited, the group stole into the ruin called Shotgun I and established a labyrinthine fantasy with false walls, colored lights, a river of discarded store mannequins and a homemade "grotto" filled with thousands of bottle caps and tented with the pink tarps left by Brad Pitt's Make It Right housing project in the devastated Ninth Ward.
I like the extraordinary caves of Anchor Church, a mile upstream from Ingleby near Derby, where the river has carved out a series of rock grottos.
Afterwards, we'd cross the river and go boating past the 19th-century grottos and waterfalls of the Lac Inferieur in the Bois de Boulogne (boats a snip at £7 an hour).
The massive residence spans more than 200 feet of Gulf of Mexico frontage a "coastal oasis" highlighted by a meandering lazy river pool with waterfall, swim-up bar, bridges and a grotto that flows through the resort-like grounds.
