Walls
When I first came to Japan, I somehow hallucinated that since buildings are generally of wood, there's no traditional stone building technique. In a region subject to frequent earthquakes, there is an obvious advantage in not making houses by piling things on top of each other and relying on weight for stability. But while the superstructure of buildings (including castles) is generally of wood, of course stone has always been used for foundations, retaining walls, and things like that.
Once this had finally dawned on me, I started noticing some interesting features. I grew up in Painswick, a stone-built village in the Cotswold Hills of South-West England, surrounded by fields edged with dry-stone walls, so I thought I knew how walls worked, but it turns out that the techniques used in the two places have almost nothing in common.
Anyway, you can see in the left photo above that some walls are simply built with the conventional "brick-wall" pattern of horizontal blocks, so why the fuss about diagonals? Isn't it just a free choice? Anyone who has ever played with children's building blocks knows that using standard "bricks" whose length is twice the width, it's trivially easy to go around a 90-degree corner. And odd angles - acute or obtuse - can be managed if you trim the ends of the block appropriately. But with diagonally laid blocks, apart from the gentlest of curves, there is simply no way to do it!
And on the left - the fastidious way! This is only a 10-degree bend in the road, and it means stopping and starting again.
(Right) Here's something different: the side of a flyover in hexagonal blocks. And oops! again...
