So, for whatever reason, I was thinking about English's weird ability to string along multiple prepositions in order to create a "customized" spatio-temporal-motivational quasi-adverbial phrase.  A typical example would be "We're coming on down for your birthday", where "on", "down" and "for" are all juxtaposed together.  I'm assuming what makes such strings possible is that various common prepositions such as "on", "off", "in", "out", "up", "down", and "through" are actually functioning as spatio-temporal-completive adverbs in these sentences, not prepositions, although it might equally be argued that the string as a whole functions as a complex, multi-part preposition (assuming it's followed by a noun or noun phrase, of course).

At any rate, I started playing around to see just what might be the longest such string possible in terms of numbers of prepositions (including those used as adverbs/complements), while still making semantic sense (at least to a native speaker).  I came up with six, shown in the following example (which hopefully is semantically acceptable to native speakers -- it is to me!)  I imagine the sentence below being used to describe, say, a rooter being threaded through the plumbing system of a house.  

     "He brought it on up inside along through within the main pipeline."

(If it doesn't seem right at first hearing, try putting a comma after the word "through".)

What's interesting is to analyze each word in the prepositional string to see exactly what it adds to the overall meaning.  (The following is my own semantic interpretation):

   "on" -- in conjunction with the verb "brought", implies translative motion toward a goal

   "up" -- either a completive/telic marker, or a spatio-temporal adverb indication the translative motion is in an upward direction. 

   "inside" -- the fact that the object is travelling inside of another object.

   "along"  -- describes a quasi-linear course

   "through" -- implies both a completive aspect as well as reinforcing translative motion while surrounded by an exterior medium

   "within" -- reinforces interiority vs. an exterior medium

Clearly, there's a lot of semantic redundancy.

I'd be curious to see if others can come up with similarly long, or even longer strings that make semantic sense.  I'm also curious as to the extent to which other Germanic languages allow such strings (...and even more curious as to whether non-Germanic, even non-IE languages, have equivalent ways of creating customized spatio-temporal descriptive phrases like this without resorting to paraphrase).

--John Q.