The Roman Empire situated an outpost at Fort Sinister in the Barbaric Archipelago for Dragon Rustling - catching dragons and shipping most back to Rome for food and goods. The Fort is equipped with at least four Observation Balloons, presumable for transport and providing a high point to watch the goings-on at the fort and surrounding areas.
The balloon crash-lands aboard The Blue Whale and the three Viking children and the Gronckle emerge unscathed.
The Roman Observation Balloon has a basket that appears to be from woven plant material, big enough to fit at least several people. It is attached to a large, inverted-pear-shaped balloon with a Roman emblem of wings on it. A caged Gronckle blows hot breath into the interior of the balloon, causing it to rise into the air.
It was empty except for a rather depressed-looking Gronckle, trapped in a cage right underneath the open mouth of the balloon. Every now and then he shot out a burst of flame that heated the air, and this would send the balloon bouncing upward for a moment before it was stopped by the rope that moored it.