JOURNEY INTO AMAZING CAVES — *** 1/2 — Large-screen documentary about cave exploration; narrated by Liam Neeson; not rated, probable G (nothing offensive).

There are moments during "Journey Into Amazing Caves" when it seems the images on the screen could have been beamed back from a planet in another solar system.

One such moment arrives as a small team of expert cave explorers lower themselves into a deep chasm below the Greenland ice cap. From the surface, it looks like they are sliding into an unimaginable void. Inside the ice cave, they dangle like spiders on silk threads, between swooping, translucent walls of blue and white.

It is a breathtaking sight, captured with awesome skill by the cinematographers of MacGillivray Freeman Films, the kings of IMAX high adventure photography.

The filmmakers behind "Everest" and "The Living Sea," among other beloved giant-screen science-and-nature films, manage to scale new heights (and plumb new depths) in their latest feature.

The movie also infuses personality and a sense of fun into the scientific story through its featured explorers, lifelong caver Nancy Aulenbach and microbiologist Hazel Barton, who studies organisms that thrive in extreme heat, cold and dark.

Together, the women rappel 300 feet down the face of the Grand Canyon to a cave-sized gash in the cliff wall, withstand blistering cold to investigate the ice cave in Greenland, and clamber through a rain forest to chart an underwater cave on the Yucatan peninsula.

The movie also serves as an appeal to protect natural caves from abuse and environmental degradation. The message can be heavy-handed, for instance, by repeatedly noting that Barton's discoveries could lead to life-saving drugs.

Liam Neeson narrates with soothing authority, and a soundtrack full of new versions of Moody Blues' songs sets a graceful tone for this engrossing look into the Earth's secret places.

"Journey Into Amazing Caves" is not rated but would probably receive a G. Running time: 40 minutes.