In terms of fictional cities there are probably few as recognizable as Gotham and Metropolis.  This is mostly as a result of their association with two of the more famous superheroes – Superman and Batman.  In terms of the cities themselves they do not really have much in common, except that they could be said to be based off of New York City.  As cities though which represent such well known fictional characters though, they do share one thing in common and that is their height, and that is a height which is massively exaggerated at times.  There are some practical reasons to this.  For about 4000 years between 2700 BC and 1300 AD Egyptian pyramids were the tallest manmade structures in the world.  From 1311 AD until 1884 various churches were the tallest structures in the world.  Only starting in 1930 with the Chrysler Building (which was surpassed a year later by the Empire State Building) were the first skyscrapers which modern technologies allowed to build far past the height of other buildings and this fascination with growing higher continued for some time.  For instance, in 1956 Frank Lloyd Wright designed a skyscraper known as the Illinois (which was never built) which would be a mile high.  Thus the height of the buildings was partly reflective of the technological and architectural impulses of the time.  However, taken from a different vantage point the height of the buildings might have helped to establish these two heroes as almost mythical characters (to which Spider-Man could also be included).  Since the ancient times height has always been something which has been associated with divinity whether it be Zeus staring down in anger from Mount Olympus or the Christian God halting the building of the Tower of Babel do to its hubristic nature (though the interpretation of this is debatable.)  Generally speaking though gods and some legendary heroes assumed positions of both physical altitude to display their power.  In the case of the two iconic DC heroes, this was likely not planned specifically for this case but it nonetheless may have helped with their establishment as nearly mythical figures.