Black Desert? The developers are getting ready to let players do just that. Sieges will be enabled on a single server on January 17th for a live test, and as long as nothing breaks horrendously, all servers will have the mechanics enabled on January 24th.
Each guild will be able to build two towers and one command center as part of the lead-in to the warfare; the last guild standing after a siege will take control of the castle and be the defenders during the next assault. Still no word has been offered on an exact date for a North American release, for those of you watching this with hungry eyes. You'll have to find out how the siege tests go from the sidelines.