It is not the old world but your could create a new world using the same world seed that your old world used.

Nothing you built in the old world will appear in the new one. Neither will any of the terraforming you may have done in the old world. The shape and positioning of landforms and biomes in the new world, even positioning of resources will be very, very similar to the old world. Since the new world will be unexplored, biome changes that were added after the creation of the old world and did not appear in explored portions of that old world, will be in the new world.

Basically, you will be starting in a virgin new world that is the same as your virgin old world except the new world will include terrain features added after the old world was created.