Seriously ancient and dense forests used to be the norm over much of the subcontinent not too many centuries ago; they were nasty enough that most armies just plain went around them if they could, for example. Increasingly populous humans with their axes have rather reduced them since then, and some climatological shifts back and forth did their part, so there's very very few patches of those antediluvian woodlands that once covered the land almost from coast to coast left now - and natural forest fires, pollution and the like in part keep them in check.

Up here in the north even the biggest trees tend to be more on the tall than massive side - probably an effect of the climate and snow - but I recall seeing some fairly imposing examples of flora in for example France so the huge RTW trees certainly are not a terrible stretch for the virtually untouched woodlands of over two millenia ago, even if they do seem a bit overblown at times.