In the Harry Potter series, Voldemort splits up his soul into 7 pieces and puts the "pieces" in objects that he hides, called horcruxes, so that one would have to "kill" all 7 horcruxes in order to kill Voldemort.

What I don't understand is Voldemort's horcrux choices. Why would he use such obvious things as large pieces of jewellery (Rowena Ravenclaw's diadem), his old diary, or even living, mortal beings like Nagini?

It seems that a safer route would have been to make a horcrux out of a single pebble and throw said pebble on a massive beach or in the ocean; this would have made it impossible for Harry to find it and thus impossible for Voldemort to die.