If no-one is harbouring any lingering desires to re-kindle the relationship, and no-one is still hurting over the breakup, then a friendship is possible. If either (or both!) or those circumstances are in place, then their is pain waiting at the end of it all, and desireable as a friendship is, in these situations it is not always possible. So, if there is no baggae hanging around, and either of you would be delighted if the other found a new partner, then go ahead. Otherwise, walk away for a year at least, then get in touch, and see how each of you is feeling. Resist the urge to imagine that because you were close as lovers it will work with you as friends. It can be done, but it's not easy, so avoid the rosy glow of planning how good it will be, and take it a step at a time, and be ready to bail if it starts going wrong.