Cassino Beach is Rio Grande at its most open and elemental: a long, flat Atlantic shore with surf, wind, beach traffic, and very little sense of enclosure. It is often promoted for its sheer length, but the better reason to go is the feeling of standing on the edge of southern Brazil.
The beach is easiest with your own transport or a clear local bus plan. In poor weather it can feel bleak; in good light it explains why Rio Grande looks outward to the water.