Hello everyone,
I would like to know if there is any tool able to extract the design from an existing Oracle database.
I have a read access to it and I would like to have the design. Or simply export it to a *.sql and then read it with any tool able to create the design with the links between the tables.
Something like that 
Thank you very much.
There are a number of tools which do reverse engineering from an Oracle database, but most require a license. Oracle has its own Data Modeller but frankly it is overpriced. If you are a site which uses TOAD then you should definitely consider Quest's TOAD Data Modeler.
There are not many free tools left on the market but SQL Power offer a community edition of its SQL Architect tool which does reverse engineering. Check it out.
Oracle SQL Data Modeler answered to all my questions.
It has a reverse engineer tool that creates the logical and physical model from the database.