Newbie Questions On British Isles Map

[Easy n Dirty]

Apologies if this is in the wrong forum, but...

What is Hadrian's Wall, and what does it enable/prevent?
If there are mountains between adjacent territories (like between Kerry and Galway), will this prevent attacks and fortifications between these territories?

Thanks in advance, and if there's somewhere I should be looking for answers to these and similar questions as I start to play on different maps, please advise.

[Haydena]

Hadrians wall is a one way border, you can attack from Northern England into Scotland but not from Scotland to Northern England. I know Asia has one like this as well from Inner Mongolia to Mongolia, but not the other way around.

And yes the mountains between adjacent territories do prevent attacks and fortifications. So make sure you watch out for them. I think almost every map has unpassable borders so make sure you're careful.

Doesn't look in the wrong section so I wouldn't worry .