A gateway or opening in a fortified place is commonly referred to as a "gatehouse" or "gate." It serves as the main entry and exit point for the fortified structure, and is usually designed with defensive features such as a portcullis or drawbridge to protect against intruders.
Gatehouse
The entrance to a building is a door.
Entrance, gateway, door
Port Royal
Port Royal
A gateway or entrance to someplace else. Be it near or far.
A bastille is a castle tower or fortified building, or a prison or jail.
A fortified town for self-defence, with entrance gates and walls.
CASTELLAN
A gate....lol
A portcullis is "a grating of iron hung over the gateway of a fortified place and lowered between grooves to prevent passage."