Correct the following run-on sentences and/or comma splices....

Beyond the forests are steep cliffs, at the bottom of the cliffs are huge, moss-covered boulders.

Again ... which comma needs to be a period?

??

To correct the run-on sentences and comma splices in the given sentence, we need to make sure that each independent clause is properly separated. Here's the corrected version:

1. Beyond the forests are steep cliffs. At the bottom of the cliffs are huge, moss-covered boulders.

Explanation:
To correct the run-on sentence, we can separate the two independent clauses into two separate sentences by adding a period (full stop) after "cliffs." This makes the first part "Beyond the forests are steep cliffs" its own complete sentence.
We can then start the second sentence, "At the bottom of the cliffs," which is another complete thought on its own. By doing this, we ensure that each sentence contains only one independent clause and is correctly punctuated.