Hello dsmccurdy92,
About halfway down the page I am linking is our documentation on landscape visibility. So, you have a landscape with a material applied to it. That is your main material that covers your entire landscape. Now, you can leave the Landscape Hole Material blank which will allow you to see through the landscape. When using the visibility tool what you are doing is creating a mask that is calculated per pixel. The pixel density is created when you create your landscape. So, you can create holes in your landscape but they will be squarish. Also the landscape is typically thin so you will not see the other side of the landscape that is facing you. It is, by design, not two sided. Geometry will be need to hide things like the jagged edges and inside of the landscape.