Aquila
Andrew Norriss Audio Book

It was a landslide! First Geoff disappeared, sliding down the hill in a rumble of thunder, then Tom followed. A moment later both boys found themselves in a cave underneath the earth, sitting opposite a skeleton dressed in armour and clutching a sword. But the really strange thing was the object just beyond: it looked like a small boat, had seats, and had these little coloured lights...

And when Geoff suggested they climb aboard, a landslide was the least of their problems.