finding the root of circular reference issues

Hello. I have an immense and complicated spreadsheet that I did not create (but am familiar with). I noticed recently that there is a circular reference error. When I look at the tabs they all have different cells with circular reference effor. I'm positive it's all related to one source, but since the spreadsheet is so complicated I'm not sure how to pinpoint what cell/s is causing the circular reference. Any advice? This is a big headache.

Ok, got it. Thanks.