in sonic's last level [level not boss] and u just get out of the area where you are surrounded by a big blue box there is a rail and if u go on the rail somewhere down there is a rocket [it will be towrds your left go on the platform use the rocket jump from platform to platform untell u see one of those rails that u use the homing attack on to go up [this isnt the one u would end up on if u just keep going the normal way] and at the top and right in front of u is it