The first sentence is certainly correct and more conventional. The second sentence seems wrong. Consider:
This structure has the length of a long tractor trailer and
the height of a large oak.
Here, "the" has the effect of comparing the length (height) in question to the length (height) of a definite or specified object.
According to this reasoning, your second sentence refers to "the width of 16 meters." What is the width of "16 meters"? "16 meters" in itself does not have a width.
To turn matters around, consider this:
This structure has a length of a long tractor trailer and a
height of a large oak.
In this case, "a length of" begs for a definite or specified length, such as "16 meters." "A long tractor trailer" is not a length. You could say, "a length of the length of a long tractor trailer," but why would you want to do that? :-)
For a discussion of definite ("the") and indefinite ("a", "an") articles, see https://en.wikipedia.org/wiki/Article_(grammar).