[blackrock]

Lava seems to destroy everything. Tectonic plates shifting would eventually turn everything over.

If the Venusians ever became atomic, and then space faring, then the best way to find evidence of them is probably in their ancient technology in space. Maybe dead satellites floating around the sun in a stable orbit. Or floating around in a geosynchronous orbit around Venus itself.

Or maybe they even sent spacecrafts to other outer planets, like Earth or Mars. I would look there, to find ancient alien Venusian technology.