Searching for a lore Accurate Size of Mumakil

[Nerwen]

Originally Posted by R.R.J Tolkien

Yes it was large enough for a tower as were African and Asian elephants.

https://en.wikipedia.org/wiki/War_elephant

I think being on the back of a large elephant alone provides the purpose of observation. A tower would add protection i think. I am not so sure how high it could be and stable upon such a beast.

Note that historical war-elephants were typically the smaller Asian species- so the tower is no indication of vast size. On the other hand, we have the author's statement (following on from your quote) that-

...the Mûmak of Harad was indeed a beast of vast bulk, and the like of him dors not walk now in Middle-earth; his kin that live now in latter days are but memories of his girth and majesty.

So we are talking about something *significantly* larger than a modern elephant. Beyond that it's hard to say exactly how large a creature Tolkien had in mind. My personal image is of something rather smaller than the movie versions, however. Perhaps it's a practical issue- I mean how would you tame those things in the first place?