How to save a scene that you randomly generated as a new level in your build settings?

I am randomly generating the overworld of my game. When the player enters a city they are loaded into a level of that city. Then when they exit the level I would like them to return to the same previously randomly generated overworld, however currently when they return it generates a new overworld.

So I suppose my question is, how would I save the generated world to return to later?

Here is how i'm generating the world.

 public class CubeGrid : MonoBehaviour {
  
     //these are now GameObjects so you can use Prefabs to define what they are
     public GameObject border;
     public GameObject grassLand;
     public GameObject house;
     public GameObject city;
     public GameObject tree;
     public GameObject wolf;
     public GameObject bandit;
  
     public int randNum = 0;
     public int xCubes;
     public int zCubes;
  
     public bool fighting = false;
     public bool enterWolf = false;
  
     void Start () {
        GenerateLandscapeAndObjects(xCubes,zCubes);
        GenerateBorder(xCubes,zCubes);
     }
  
     private void GenerateLandscapeAndObjects(int xMax, int zMax) {
  
        GameObject landscape = new GameObject("Landscape and Objects");
  
        for ( int z = 0; z < zMax; z++ )
        {
          for ( int x = 0; x < xMax; x++ )
          {
           float rnd = Random.value;
           if ( rnd < 0.01 )
           {
               DoInstantiate(city, new Vector3(x, 0, z), Quaternion.identity,landscape.transform);
           }
           else if (rnd < 0.07)
           {
               DoInstantiate(tree, new Vector3(x,0,z), Quaternion.identity,landscape.transform);
           }
           else if ( rnd < 0.15 )
           {
               DoInstantiate(house, new Vector3(x, 0, z), Quaternion.identity,landscape.transform);
           }
           else 
           {
               DoInstantiate(grassLand, new Vector3(x, 0, z), Quaternion.identity,landscape.transform);
  
               randNum = Random.Range(0,50);
               if(randNum <= 3){
                  DoInstantiate(wolf,new Vector3(x,0,z), Quaternion.identity,landscape.transform);
               }
               else if(randNum ==4){
                  DoInstantiate(bandit, new Vector3(x,0,z), Quaternion.identity,landscape.transform);
               }
           }
          }
        }
     }
  
     private void GenerateBorder(int xMax, int zMax) {
  
        GameObject borderGameObject = new GameObject("Landscape and Objects");
  
        for ( int x = 0; x < xMax; x++ )
        {
          DoInstantiate(border, new Vector3(x,1,0), Quaternion.identity,borderGameObject.transform);
          DoInstantiate(border, new Vector3(x,1,zMax), Quaternion.identity,borderGameObject.transform);
        }
  
        //create border blocks along z axes
        for ( int z = 0; z < zMax; z++ )
        {
          DoInstantiate(border, new Vector3(0,1,z), Quaternion.identity,borderGameObject.transform);
          DoInstantiate(border, new Vector3(xMax,1,z), Quaternion.identity,borderGameObject.transform);
        }
     }
  
     private void DoInstantiate(GameObject prefab, Vector3 position, Quaternion rotation, Transform parent) {
        Transform temp = ((GameObject)Instantiate(prefab,position,rotation)).transform;
        temp.parent = parent;
     }

Heres how I get inside buildings

        if(guiOn && enterCity == true)
        { 
          if(GUI.Button(new Rect(10,200,1200,100), "Visit the inn"))
          {
           Application.LoadLevel("InsideTheInn");
          }

And heres how I return to the overworld.

 public class InnCameraScript : MonoBehaviour {
  
     void OnGUI(){
        if(GUI.Button(new Rect(10,400,1200,100), "Leave the tavern.")){
        }
        Application.LoadLevel("Map Creator");
     }
 }

However obviously that's where it creates a new map because its loading the first script again.

So my question is how would I make that first script save the world it generated as a new level in the build settings so that I could refer to it later in scripts similar to the third script I posted.