Hi, long long ago I've played this server. It's like towny I guess? You need to get money to make a town (as a start) but you can also make a castle (which builds his own) with items you bought/created. I forgot the name of the server but I would love to play it again.
You could also expand and defend you castle by making scout towers or archer towers.

Here are 2 screenshots, does anyone know which server this is?
http://imgur.com/NJHVHzX
http://imgur.com/8lB4AZa