Why not, you are not going to have a city with buildings say 10 stories tall but walls, or sides 1500 miles tall. if the walls are 1500 miles tall then there will be floors and activities that high (or close to it) as well in parts of the city at least if not all of it.
The walls are not 1500 miles tall
Rev 21:17 And he measured the wall thereof, an hundred and forty and four cubits, according to the measure of a man, that is, of the angel.
and the height of the city can also be figurative rather than literal:
G5311
ὕψος
hupsos
hoop'-sos
From a derivative of G5228; elevation, that is, (abstractly) altitude, (specifically) the sky,
or (figuratively) dignity: - be exalted, height, (on) high.
Barnes:
According to this representation, the height of the city, not of the walls (compare Rev_21:17), would be three hundred and seventy-five miles. Of course, this cannot be understood literally, and the very idea of a literal fulfillment of this shows the absurdity of that method of interpretation. The idea intended to be conveyed by this immense height would seem to be that it would contain countless numbers of inhabitants. It is true that such a structure has not existed, and that a city of such a height may seem to be out of all proportion; but we are to remember:
(a) that this is a “symbol”; and,
(b) that, considered as one mass or pile of buildings, it may not seem to be out of proportion. It is no uncommon thing that a house should be as high as it is long or broad.
The idea of vastness and of capacity is the main idea designed to be represented. The image before the mind is, that the numbers of the redeemed will be immense.