ora-01775

How to debug ORA-01775: looping chain of synonyms?

I'm familiar with the issue behind ORA-01775: looping chain of synonyms, but is there any trick to debugging it, or do I just have to "create or replace" my way out of it? Is there a way to query the schema or whatever to find out what the current definition of a public synonym is? Even more awesome would be a graphical tool, but a...