What are some of the most interesting [optical] illusions that you know of involving language (in any script; e.g. Arabic, Chinese, Cherokee, Latin, Japanese, &c.)?

Answer 1

This may not constitute an 'illusion' quite in the way you mean but often in Latin, because the order of words is relatively free, "word pictures" can be made which emphasize or embellish the language.

For instance, in an early section of the Aeneid we read:

Aeoliam venit. Hic vasto rex Aeolus antro (52)

Because 'vasto' (empty, deserted, devastated) modifies 'antro' (cave, grotto) while at the same time being placed on either side of 'rex Aeolus', a kind of "word picture" is formed. The king Aeolus sits withing an empty cave. In good English the line states:

She came to Aeolia. Here in an empty cave the king Aeolus

But if we maintain the order of the Latin original:

She came to Aeolia. Here in an empty the king Aeolus cave

Note that 'empty' still modifies 'cave'.

Hence a kind of 'illusion' whereby the words, as they hit the ear of the listener, form a picture of the thing described.