When it comes to describing something as dependable and sturdy, the phrase "more rock solid" may seem like the ultimate compliment. However, there are plenty of other synonyms that can convey the same level of strength and resilience. "Unshakable," "invincible," and "indestructible" all suggest that a particular object or concept is utterly impervious to damage or disruption. "Firm" and "immutable," on the other hand, imply a more subtle sense of stability and steadfastness. Ultimately, the choice of synonym depends on the context and the desired connotations - whether one is describing a physical structure, an emotional bond, or a moral principle.