Hey,KoleyKole28,you can do (if you have MCEdit) a big box with walls and ceiling made out of glass(like a glass box),then you can make a catle gate like in Mumbo Jumbo's video(or alternative).
Then,you can build a castle,roads,houses(medievals ones in your case) etc.
If the server is online,I can help you.
Thx for reading this.