Which Way Should I Face?

The halacha as we all know is that when one davens he should face Yerushalayim. Even if the Aron Kodesh is not in the direction of Yerushalayim, we still must face Yerushalayim. In my neighborhood there is one shul where I see the people angling themselves to the right of the Aron Kodesh, ostensibly because that is the exact direction towards Yerushalayim. There is another shul up the block but aligned with the first shul where people angle themselves to the left of the Aron Kodesh ... which makes me wonder.

What is the exact direction of Yerushalayim???

See Piskei Tshuvos Vol. 1 page 738 for sources on this law. Incidentally, the implication of the Rambam in his Sefer Hamitzvos is that the law of facing Yerushalayim is mi-dioraisa. It is discussed here.