Life can be full of let-downs and disappointments - the first time you taste beer as a teenager and wonder what all the fuss is about; that feeling when you open a giant parcel to find a tiny gift and an awful lot of plastic packaging inside; that first date, soon abandoned, with the guy who, it transpires, looks nothing like his Tinder profile.
The world of travel is not immune to such shortcomings. The breathless opinions of your friends and the hyperbole of glossy brochures might lead you to believe that such and such city/hotel/restaurant is the greatest thing in all eternity - only for your own experience to unearth a crime-ridden hellhole/rat-infested hovel/overpriced mess of posing hipsters, rude waiters and food which is as bland as the portions are miniscule.
Then there are the landmarks which are very famous and very busy - but which, on close inspection, turn out to be rather smaller than legend has it. Not in terms of popularity or the number of other tourists clustered around, but in actual physical size.
Take Stonehenge as an example. There it is above, as postcards intended - the very image of Bronze Age Britain at its most romantic. It looks huge, seismic, a timeless temple assembled by the hands of neolithic giants. It is only when you see it in person - or when a load of Summer Solstice revellers are allowed to go goo-goo for the sun in the middle of the main circle - that you realise those colossal slabs are not quite as colossal as you might think. Each standing stone measures 13ft (4.1m) - roughly the combined height of two averagely tall men. Impressive but not gargantuan.
The Little Mermaid
Tourists flock in their thousands to this celebrated statue, which sits on the Langelinie promenade in Copenhagen. A representation of the titular heroine of one of Hans Christian Andersen's most affecting fairytales, she sits a reasonable walk - about two miles - from the centre of town, but many visitors still make the hike in search of her.
It is only when they arrive that they realise the mermaid really is little. Specifically, she is about 4.1ft (1.25m) in "height". Better hope your camera has a decent zoom feature.
Belgium keeps it mildly weird at the heart of its capital, where the notorious fountain of a small naked boy merrily urinating is a constant source of camera clickery.
How small? A mere 61cm of sculpted bronze. Don't plan a weekend in Brussels around it.
By artistic definitions, Leonardo Da Vinci's 1503 depiction of silk merchant's wife Lisa del Giocondo is a Renaissance titan - a captivating creation on canvas so sizeable in impact, influence and fame that it practically has its own gravitational field.
It is only when you try to gain a glimpse of that slight smile, pushing your way through the crowds in the Louvre, that you realise just how small "La Gioconda" is in the flesh. Specifically, the painting measures 77 cm × 53 cm. Watch where you're waving that selfie-stick, you almost had my eye out.
The companion-piece to the pyramids of Giza was hewn from the limestone of ancient Egypt by the gods who oversaw this early civilisation. They created a figure of size and splendour, part human, part lion, to inspire awe and devotion through the ages.
Well, that's roughly the spiel. In fact, Cairo's most notable cat-man hybrid is significantly smaller than the fabled tombs it loiters next to. Its statistics - 238ft (73 m) long, 66ft (20m) high - mean it is big, but nothing like as large as many imagine. Oh, and it was made by mortal craftsmen some time between 2558 and 2532 BC.
Christ The Redeemer
Never has one statue dominated a city's skyline as much as Cristo Redentor - soaring above the beaches, bars and barrios of Rio de Janeiro, the crowning glory atop the swarthy jungle-clad peak Corcovado.
What do you find when you reach the top of the mountain? The slightly deflating truth that this particular Christ is a "mere" 98ft (30m) in stature. To put this in context, the Eiffel Tower prods the clouds at 1,063 ft (324m). Now that is an urban giant.
The Statue of Liberty
The same case of slight return perhaps applies to the most famous American lady who is carved from copper and lives on an island opposite the skyscrapers of lower Manhattan.
Again, it is not that Liberty is tiny. The statue, to the tip of the torch, measures 151ft (46m). The whole construction from ground level up is 305ft (93m). And yet, all those representations in films, TV shows and American mythology leave you expecting just a little more.
It is not that this feature is determined to lambast America's most noted landmarks. "You call that big? That's not big. I should have gone to Russia."
It's just that, for all its image as a Grand Canyon of the US north-east, all frothing water and clouds of spray, Niagara Falls is not really in the top league of waterfalls. At least, not when it comes to height. Consider these numbers. The Horseshoe Falls segment of Niagara Falls drops 188ft (57m). Victoria Falls in Zambia and Zimbabwe manages a plunge of 355ft (108m). Angel Falls in Venezuela goes the whole hog at 3,212 ft (979m).
The Blue Lagoon
No visit to Iceland can be complete without a dip in this well-named attraction about 25 miles outside Reykjavik. With good reason. The water is indeed blue (or appears to be). It is also warm. People bathe in its soothing heat and feel happy - seemingly ensconced in a steaming inland ocean. Look at the picture above for proof.
This is all fine and dandy. It is only when you see a wider photo of the lagoon that you realise it is a) not huge and b) an off-shoot of the adjacent Svartsengi geothermal power plant.