“The White Diamond” begins like a normal documentary. Over a montage of black-and-white archival footage, a wry voiceover ruminates on man’s desire for flight. The tone is ironic, apocalyptic; the sequence terminates in a close-up of the Hindenberg aflame. We are then led through the workshop of Graham Dorrington, designer of flying machines. Among other things, the title of the film refers to his latest prototype, a small, highly mobile, pear-shaped blimp.

Not your average British eccentric, Mr. Dorrington is an alarmingly intense, bug-eyed dreamer. He is also a man in the grip of a nightmare. Some years ago he designed a lightweight aircraft for Dieter Plage, a nature documentarian, and accompanied him on an expedition to the rain forest in Sumatra. Up above the canopy, a mechanical failure coincided with sudden bad weather. Plage fell to his death.

“The White Diamond” follows Mr. Dorrington’s emotionally fraught plans to float his new invention over the rain forests of Guyana. The venture was funded by a German film company in tribute to Plage, and one of their employees suggested his father shoot a documentary. All of which sounds conventional enough, except that the filmmaker happened to be Werner Herzog.

And so “The White Diamond” is no ordinary documentary but a bold and batty cine-essay on familiar Herzog themes: the doomed, visionary hero; adventure in an exotic landscape; the limits of perception and imagination. Something of a poetic gloss on “Fitzcarraldo,” it’s the perfect project for a filmmaker ever drawn to the extravagant gesture and oversized challenge. “There’s such a thing as follies,” Mr. Herzog says after a disastrous test flight of the little blimp, “I know that.”

He also knows how to make singularly fascinating documentaries. If “The White Diamond” starts off in familiar territory, it soon ventures off into terra incognita – literally so at the edge of the grand Kaieteur waterfall. Behind its roaring white curtain, in a cave never seen by human eyes, a vast flock of swifts famously make their nest. A member of the film crew, armed with a small digital camera, lowers himself next to the opening. When he returns, his director refuses to share the footage out of respect for local customs, the mysteries of nature, and, no doubt, his own perverse genius for showmanship.

The Kaieteur Falls provide this staggeringly beautiful film with a number of its most striking images and provide a stage for its single most memorable scene. Mr. Herzog joins Mark Anthony Yhap, a local hired to assist the pro duction, on a quest for medicinal plants. At a ledge overlooking the falls, the camera magnifies its reflected image in a drop of water clinging to the tip of a leaf. “Do you see a whole universe in this drop of water?” Mr. Herzog asks in his inimitably accented, unabashedly grandiose manner. Affable Mr. Yhap takes a moment before replying, “I cannot hear what you say for the thunder that you are.”

That’s him all right: a storm of an artist, full of rhetorical thunder and pictorial lightning. “The White Diamond” arranges Big Ideas into an intuitive, ideogramatic structure; this is a poem on Man, Nature, Cinema, and the Burden of Dreams. As in the best of Herzog, the filmmaking is vigorous and muscular, thrust forward by a ranging masculine energy. Yet there is also a delicate, lyrical impulse, and in Mr. Dorrington an unusually gentle hero for the director who claimed Klaus Kinski for his muse.

This is the first of two Herzog documentaries opening at Film Forum this month. A third, the Sundance sensation “Grizzly Man,” will open by the end of summer. If “The White Diamond” is any indication of things to come, the gonzo visionary of the New German Cinema may have pulled off the documentary feat of the year – three times over.

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