Entrance Gate to Old Fort Niagara

As you go into Old Fort Niagara north of Niagara Falls in Upstate ny,  you go through the gatehouse or gate entrance to the fort. Here is a massive stone structure with a door that closes up on chains like a European Castle. The beam above the doorway and shield declare it to be the French Fort “Porte Des Sinonations” 1678-1759. The fort was taken over by the British after that and after the War of 1812 was turned over to the United States.  I thought the architecture was interesting as they originally had a rounded roof supports of stone with a log roof. I wonder if the logs originally ran the other way and followed the curve? Note the stone gutters.