This is for giant items like monuments, obelisks, etc.

If you just need to move a big boulder (say the size of a small desk) on your property, it's relatively easy to use a big lever and fulcrum to lift an edge of the boulder, wedge some rocks under that edge to keep it lifted, reposition the lever deeper under the boulder, and keep lifting and wedging, until the whole boulder flips over. Repeat. Taught to me by my housekeeper who used to move boulders with her father in Mexico.