How to set limits to where player can go

Hi. I am not good at this but I hope you can understand what I am asking.
I am trying to set up a script that is equipped to my player object(currently this is
the default 3rd person controller) and I have myself a primitive town builtplan to create most of the models in blender and I have it set up so that the player can roam freely around the terrain of the town. What I need though is a way to set up an invisable collision box type thing so that the player cannot go past a certain point.

I am trying to use a simple x1,x2,z1,z2 setup stating that if the player goes past x1 the player is stuck there and can’t go further. This is what I was thinking it should look like say x1 = -85, x2 = 85, z1 = -75, z2 = 75

now if the player goes past x1 they are stuck at -85 on the x axis and so on.

So how can I set this up. keep in mind I am using Java in Unity. I am most comfortable with it.

I’m sure I could use Geometry to do this but I am trying to avoid using geometry as it can look really fake when the player touches the wall.

I hope this makes sense and I hope someone can point me in the right direction.

For invisible walls I would simply create an Empty in the scene and add a collider to it. You can surely also do it with scripts, but that would be very complicated, depending on the complexity of your terrain.

Just put a meshcollider object with no renderer attached to block the player from entering where he is not supposed to enter.
The player then would be able to cross one way only - into the inside along the normal and would be blocked to the outside which is against the normal.

I figured it out guys. I was hopeing I could delete this before someone answered. I used the respawn method. the script looks like this now.

//This will keep the player from going past a certain point. Think of it as a collision box without geometry

function Update () {    
	var myPosX = transform.position.x;        
	var myPosZ = transform.position.z;        
	Debug.Log("x: " + myPosX + " / z: " + myPosZ);
	if(myPosX <= -85){
		transform.position.x =-85;

So I am sorry for wasting your precious time guys. Thanks for the help though.

what would i do if i had a paddle and it went through the floors.