The ark in a synagogue is known as the aron kodesh (holy cabinet). It is an ornamental closet built in all synagogues, which contains the synagogue's Torah scrolls . When possible, the Ark is located on the wall of the synagogue which is closest to Jerusalem because according to Judaism, Jerusalem is the holiest place in the world.

Examples of aron kodesh~~

Virtual Synagogue • Sacred Objects

Wellesley Middle School
February 2006

Sources:
http://www.answers.com/main/ntquery?method=4&dsid=2222&dekey
=Ark+%28synagogue%29&gwp=8&curtab=2222_1&linktext=ark