Visualizer

Hello everybody,

I have got an already existing Porstgres DB which is pretty large
(including more than 650 table with considerable number of constraints
etc). And now I am supposed to realize generally how it is constructed
and works. I thought it would be good to have a grapahical
visualization of whole DB (with tables and relations etc). Does anyone
have any idea about any tool that does this? I would also appreciate
any comments or suggestions that might help me in this regard.

Thank you in advance,
Ali.