From what I thought a long time ago, the main point of a sentence is contained in the top level clause. That makes me question whether one can use a statement following a relative pronoun to end a sentence, and to make that clause the most meaningful information in the sentence. For instance, if I say, The city descended and stood on a new planet, which was becoming home to the people who escaped from earth. The main statement in the sentence is "The city descended and stood on a new planet", but there is meaningful information that is subordinate to it, which ends the sentence as though it were the main information. The new information is always to supposed to come at the end, so the main clause is leading into the relative one. Is this acceptable?
I see nothing wrong with what you have. The only thing I'll mention is that "which" is referring to "planet" here. I'm not sure if that's what you wanted, so I thought I'd mention it.
Hi Waitingforzion, In typical sentence structure, it is generally recommended that the subject is placed at the beginning and new information comes at the end. This kind of makes understanding the sentence simpler, because it tells your reader right away who is doing the action of the sentence or what is being described. That is not the only construction possible, though; as with so many other things in writing, the rules here are bendable. However, with your example sentence, the subject is the location, not the people. If that was your intention, great! If not, some reconstruction may help. The people fled to the city that stood on a strange new planet after escaping Earth. Or The people escaped Earth only to find themselves in a new city on a different planet. Eh, maybe those are not the most beautiful sentences in the world, but hopefully they illustrate my point. The subject in each is now the people, rather than the city. Do keep in mind, too, that by saying the planet is "new" what you are actually saying is that it is freshly minted---hot out of the universe's oven. If you are trying to say that the planet is new to the people, the word "different" is a better adjective, or any number of other words to describe it (even the plant's name could be substituted here). If you want to maintain the subject as being the city, you can leave it how you have it (aside from the "which" that should probably be changed to a "that" just as Thirdwind pointed out) or you can add the additional information about the people with a nonrestrictive "which" phrase, like so: The city, which had become home to the people who had escaped from Earth, descended and stood on a new planet. Again, the word "new" causes trouble, because surely the planet is not new to the city that stands upon it. Here is a little shift in the structure that might work for your sentence: The city on planet Zarkon was now home to the people, who had fled planet Earth. "The city on planet Zarkon" is working as a phrase here, allowing our subject to remain the people. Eh, it moved the subject further along the sentence. (You could lose that comma and change the meaning of the sentence a little. The comma makes the phrase "who had fled planet Earth" restrictive; ALL the people had come from planet Earth, and Zarkon was now home to ALL of them. Without the coma, the phrase is nonrestrictive; Zarkon was home to the people who had fled from planet Earth, but not to the others who had come from someplace else. This is one of the reasons why punctuation is so important!) Hope this helps.