In some senses, a waterfall is the planet at its most rudimentary.
Even the grandest of cascades is, after all, a simple case of physics - the raw effect of gravity on one of the most intrinsic elements of life in our world, no more remarkable than a summer raindrop, or a persistently leaky roof.
And yet to reduce these roaring "landmarks" to examples of cause and effect is to ignore their majesty.
The waterfall has always captured the imagination. Witness the words of David Livingstone - not a man given to hyperbole - on seeing what he would call Victoria Falls, on November 16 1855: "Creeping with awe to the verge, I peered down into a large rent which had been made from bank to bank of the broad Zambezi... No one can imagine the beauty of the view from anything witnessed in England. It had never been seen before by European eyes, but scenes so lovely must have been gazed upon by angels in their flight."
In short, a major waterfall is likely to be the centrepoint of any holiday journey.
The following selection of watery wonders includes some of the global classics, but also a natural marvel a little closer to home...
1. Kaieteur Falls, Guyana
If you could custom-build the perfect waterfall, it might resemble Kaieteur Falls. Tucked away at the heart of Guyana, on the north-east shoulder of South America, this is the waterfall as supermodel - a single curtain of liquid where the River Potaro slips 741ft (226m) into a forested chasm. Remoteness only adds to its splendour - it is most easily reached via a nearby airstrip (the alternative is a three-day overland journey). Yet it is not so jungle-clad as to be beyond approach.
2. Angel Falls, Venezuela
Just 215 miles separate Kaieteur and Angel Falls, though the latter has the bigger profile. Rearing proud in Canaima National Park, in the easterly Gran Sabana area of Venezuela, it is considered the world's tallest waterfall - a spectacle where the River Kerep plunges 3,212ft (979m) (2,648ft/807m of this as an uninterrupted drop). This is thanks to the drama of a landscape where vast tepuis (tabletop mountains, in this case the noble Auyantepui) throw out a series of sheer faces. The whole scene is best viewed between June and December, when both waterfall and river are at their fullest.
3. Iguassu Falls, Brazil and Argentina
South America also works its magic farther south, where the renowned Iguassu Falls are among the planet's most spectacular border spots - foaming furiously to help the River Iguassu split Brazil from Argentina. Here, the prescient factor is not height (269ft/82m) but width, this spray-soaked showpiece stretching out for 1.7 miles. The focal point is the Garganta del Diablo (Devil's Throat) - a 2,297ft (700m) U-shaped half-bowl where the relentless power of the river is almost unnerving.
4. Tugela Falls, South Africa
This column of water crashes 3,110ft (948m) in Royal Natal National Park, a highlight of KwaZulu-Natal province, South Africa. Officially, this makes it 102ft (31m) shorter than the Angel Falls in Venezuela, though doubts have been raised by some about the exact measurements of the latter. What is not debated, however, is the sheer glory of this African vista as the River Tugela pours over The Amphitheatre - a cliff face in the Drakensberg range that can be hiked by those of decent fitness (see royalnatal.info).
5. Victoria Falls, Zimbabwe and Zambia
As in Livingstone's day, Victoria Falls is Africa's A-list waterfall. It is also the world's biggest, if you take into account a combination of height (354ft/108m) and width (5,604ft/1,708m). Its aura is encapsulated by its indigenous name (in the Tonga language), Mosi-oa-Tunya - The Smoke That Thunders. Brave souls can go further than Livingstone by swimming in the Devil's Pool - a pocket of water on the edge of the abyss where a rock ledge and a lull in the currents keep you safe. Others may prefer to watch from a discreet distance - especially from February to May, when the Zambezi is at its most swollen.
6. Niagara Falls, US and Canada
North America's most recognisable waterfall may also be the world's most famous - even if its size cannot match its reputation. In relation to other water icons, Niagara Falls is a stripling of 167ft (51m) in height - so small that, on visiting Iguassu Falls, the then-US First Lady Eleanor Roosevelt reputedly exclaimed, "Poor Niagara!" However, issues of stature do not damage the visual experience: the River Niagara zipping over the falls' three distinct cascades in a place that is as crucial to the US soul as the Statue of Liberty. That said, the view from Canada is prettier.