Do You See What This Pasco Wall is Made of?

I was taking a walk around the block during lunch and I walked past a concrete retaining wall, only to realize it wasn't it wasn't what I thought! Take a close look at these photos and see if you can guess what this wall/fence is made of!

They're sepulchres for the Columbia Memorial Gardens next door! In one of the photos you can clearly see the trays for holding the cadavers stacked up behind the wall! How macabre!