IsthmusTwo is a revision of one of my first random map scripts (and one of my favorites), Isthmus. Isthmus is a novel design which creates new playing strategies. Players start on opposing land masses, placed by teams, and separated by water. There is a central isthmus which connects all teams and divides the sea. The seas are harder for one team or player to dominate since it is divided. The isthmus is the scene for battles as the only land connection between the players. There is random variation of terrain types on this map (but no snow terrains).
This upgrade focuses on several features. The original map was released over 1 year ago, and I have learned much about scripting maps since then! The one complaint I have heard about the original map is that the isthmus was too narrow, making it easy to wall off, so the width of the isthmus is increased. The amount of fish is increased slightly. The way that the resources were placed on the isthmus was improved and they appear consistantly now. There are now forest patches on the isthmus, as well as terrain patches for improved appearance. I have increased the number of different random terrain patterns for aesthetic reasons (but no snow patterns).
I suggest you play this map at a size appropriate for the number of players so that the isthmus will place properly. Note that the script can handle any number of players on a 2 team game, and can handle a 3 team game well if 1x1x1 or 2x2x2. If a 3 team game, there are 3 seas divided by 3 bands of land joining at the center. Four team games don't always have a fair or balanced start.
Strategies for this map include going all out for a land flush (but knowing that the opponent could wall you off), boat booming, galley rushing, turtling, and others. This is an especially great map for team play. An important strategy decision is whether to have the whole team try to control one of the seas, assuring control, or to try to control both of them with the risk of not controlling either. Civs without cannon galleon are at a disadvantage in the later stages of the game, since these ships help to control the isthmus, but such civs could do well as part of a team that splits responsibility.
Resources are fairly standard (with 2 extra gold, 2 extra stone and 2 extra forage patches on the isthmus). Fish and shorefish are increased slightly over the ES norm. The computer AI handles this map fairly well, frequently walling off the isthmus, and often but not always building a 'two ocean navy'.
See here for a post with graphics: http://mrfixitonline.com/readPosting.asp?PostingId=567138