add the model

app/models/map.rb

@@ -0,0 +1,2 @@
+class Map < ActiveRecord::Base
+end

db/migrate/012_create_maps.rb

@@ -0,0 +1,11 @@
+class CreateMaps < ActiveRecord::Migration
+  def self.up
+    create_table :maps do |t|
+      # t.column :name, :string
+    end
+  end
+
+  def self.down
+    drop_table :maps
+  end
+end