Haha, a collapse! You have a wonderful perspective.
You used to be able to build a door into the wall to allow access. I haven't tried this in some time.
You can "deconstruct" the rock.
Open biy_glossary.txt, scroll down to just above "[SUBMENU_END:kota]"
Add a new line and put
.Big Rock .
save and close the file. Now when standing next to the Big Rock open the building menu and choose deconstruct and pick a rock
Note: use f3 on the item to see the name as it may be High Wall or something else, not played in a while.