"Grass is near..." sounds odd. With countable nouns you can use this construct both with definite and indefinite forms: "A boy is near..." or "The boy is near...". But with noncountable nouns, only the definite version works: "The grass is near...", the indefinite doesn't. Since the definite version doesn't capture the meaning of the Russian sentence, I would go for "There is grass near..."
my guess is that, if you wanted to say "castle grass", that would translate as "трава дворца" because the "owner" in genitive should be placed after the "owned".
so if you would say "there is a dog near the palace grass" it would be " возле травы дворца собaка".
... i think