This place is mostly well known for its famous annual mourning parade in Muharram month, a sacred month in lunar calendar between shia muslims. The mosque organizes this event each year and around 1 million people attend the event. Even people from neighbor countries gather on this event on that special date and make different type of donations.
The building itself is situated in the southern part of the city in a very traditional neighborhood. The main building is quite an old one(with almost 150 years of history behind it) and recently thanks to donations from people they extended the building and make some renovations inside it. If you want to see some islamic architecture and get more info regarding its parade, it is a very good place to stop by.