As Kratos leaves the Temple of Euryale, he comes to a round chamber with a lever. He pulls it, which then causes the stone floor to begin rising and a pack of Rabid Hounds to drop down from above, this place is known as the Stone Crusher.
In order to proceed, Kratos must kill the hounds, and then use his brute strength to prevent being crushed between the ceiling and the rising floor. If done correctly, Kratos will push the floor back down a bit, and partially open up the doorway into the corridor beyond. Kratos must repeat the process of killing hounds, and then pressing the floor back, until there's a big enough opening in the doorway to for him to slip through. This will then bring him to the Catacombs of the Fallen.