Fort Sinister is a fortress owned and operated by the Romans in How to Speak Dragonese.
Fort Sinister was built by the Romans and is their refuge in the Archipelago, outside the Roman Empire. Fort sinister covered the entirety of the tiny island it was built on in the central part of Mazy Multitudes, south of the Isle of Berk
The building is huge and very well guarded. The only way to get in is through a channel, which can flows directly from the sea. The fortress like castle has each of its sides end in high walls, which at equal distances from each other high watchtowers. Fort Sinister has many amenities such as:
- Observation Balloons as a look out for any unusual activities such as escapees and war parties
- Dragons' Cages
- Soldiers' Barracks
- Residential buildings
- Fat Counsel's Headquarters
- Prison Tower. This is where Hiccup, Fishlegs and Camicazi are imprisoned.
- The Great Amphitheater, where games are held.
The Great Amphitheater is a place which hosts regular gladiator fights and other spectacles. The Arena can be dry or flooded, and it has at the top a metal grate, preventing the escape of dragons (the walls are still too high to be able to escape from it people). Around the arena stands a huge auditorium, which can accommodate thousands of Romans.
The prison tower is packed with the purpose for which they are held slaves, criminals, gladiators or simply prisoners. Small windows overlook the ocean and are placed too high to try to escape from them.
In How to Speak Dragonese, Hiccup, Fishlegs and Camicazi are held prisoner here as part of a plan hatched by Alvin the Treacherous in the form of the Thin Prefect. The three manage to escape at the end of the book when the Romans surrender and Hiccup defeats Alvin by kicking him off the Hot Air Balloon they were using to leave.
Fort Sinister is mentioned in How to Twist a Dragon's Tale as being torn down and abandoned by the Romans. It is also the place were Alvin the Treacherous nursed himself back to health after the incident with the Sharkworms.