Well Imperator titans have a whole gothic castle on their backs. Orbital satelite imagery is quite good even in our days, unless you meant seen unaided by any mechanical means.
But I vaguely recall mentions of Land trains on medusa as well, though its not likely battle trains alike what the squats had. Finished Predator Cities btw, they should quite please any warhammer fans. Hunting old tech (archaeotech for the 40kers) is a major point of them.
But to get back to such land behemoths, the Imperial Guard still retains the Leviathan command center which shares much in appearances with the squat colossus. I vaguely seem to recall that the imperium originally got it from the squats?