diff -Nur -X/mnt/data/freeciv-dev/freeciv/diff_ignore freeciv/common/map.c modciv/common/map.c
--- freeciv/common/map.c	Sun May  6 01:54:28 2001
+++ modciv/common/map.c	Sun May  6 02:02:54 2001
@@ -1182,3 +1182,64 @@
 
   return TRUE;
 }
+
+
+/**************************************************************************
+Returns whether the tile was modified.
+**************************************************************************/
+int remove_illegal_specials(int x, int y)
+{
+  struct tile *ptile = map_get_tile(x, y);
+  int terrain = ptile->terrain;
+  struct tile_type *type = get_tile_type(terrain);
+
+  int changed = 0;
+
+  if (terrain == T_OCEAN) {
+    int illegal_specials = S_ROAD | S_IRRIGATION | S_RAILROAD | S_MINE
+      | S_POLLUTION | S_HUT | S_FORTRESS | S_RIVER | S_FARMLAND
+      | S_AIRBASE | S_FALLOUT;
+
+    if (ptile->special & illegal_specials) {
+      ptile->special &= ~illegal_specials;
+      changed = 1;
+    }
+  }
+
+  if (ptile->special & S_RAILROAD
+      && !(ptile->special & S_ROAD)) {
+    map_set_special(x, y, S_ROAD);
+    changed = 1;
+  }
+
+  if (ptile->special & S_MINE
+      && terrain != type->mining_result) {
+    map_clear_special(x, y, S_MINE);
+    changed = 1;
+  }
+
+  if (ptile->special & S_FARMLAND
+      && !(ptile->special & S_IRRIGATION)) {
+    map_set_special(x, y, S_IRRIGATION);
+    changed = 1;
+  }
+
+  if ((ptile->special & S_IRRIGATION || ptile->special & S_FARMLAND)
+      && terrain != type->irrigation_result) {
+    map_clear_special(x, y, S_IRRIGATION);
+    map_clear_special(x, y, S_FARMLAND);
+    changed = 1;
+  }
+
+  if (ptile->special & S_MINE && ptile->special & S_IRRIGATION) {
+    map_clear_special(x, y, S_MINE);
+    changed = 1;
+  }
+
+  if (ptile->special & S_SPECIAL_1 && ptile->special & S_SPECIAL_2) {
+    map_clear_special(x, y, S_SPECIAL_2);
+    changed = 1;
+  }
+
+  return changed;
+}
diff -Nur -X/mnt/data/freeciv-dev/freeciv/diff_ignore freeciv/common/map.h modciv/common/map.h
--- freeciv/common/map.h	Sun May  6 01:54:31 2001
+++ modciv/common/map.h	Sun May  6 02:02:59 2001
@@ -235,6 +235,7 @@
 char *map_get_infrastructure_text(int spe);
 int map_get_infrastructure_prerequisite(int spe);
 int get_preferred_pillage(int pset);
+int remove_illegal_specials(int x, int y);
 
 void map_irrigate_tile(int x, int y);
 void map_mine_tile(int x, int y);
diff -Nur -X/mnt/data/freeciv-dev/freeciv/diff_ignore freeciv/server/maphand.c modciv/server/maphand.c
--- freeciv/server/maphand.c	Sun May  6 01:54:36 2001
+++ modciv/server/maphand.c	Sun May  6 02:03:03 2001
@@ -53,6 +53,19 @@
 static int map_get_seen(int x, int y, int playerid);
 
 /**************************************************************************
+...
+**************************************************************************/
+static void check_terrain_specials(void)
+{
+  whole_map_iterate(x, y) {
+    if (remove_illegal_specials(x, y)) {
+      send_tile_info(NULL, x, y);
+      freelog(LOG_DEBUG, "Illegal special removed at %d,%d", x, y);
+    }
+  } whole_map_iterate_end;
+}
+
+/**************************************************************************
 Used only in global_warming() and nuclear_winter() below.
 **************************************************************************/
 static int is_terrain_ecologically_wet(int x, int y)
@@ -120,6 +133,8 @@
     }
   }
 
+  check_terrain_specials();
+
   notify_player_ex(0, -1, -1, E_GLOBAL_ECO,
 		   _("Game: Global warming has occurred!"));
   notify_player(0, _("Game: Coastlines have been flooded and vast "
@@ -166,6 +181,8 @@
       } unit_list_iterate_end;
     }
   }
+
+  check_terrain_specials();
 
   notify_player_ex(0, -1, -1, E_GLOBAL_ECO,
 		   _("Game: Nuclear winter has occurred!"));
diff -Nur -X/mnt/data/freeciv-dev/freeciv/diff_ignore freeciv/server/savegame.c modciv/server/savegame.c
--- freeciv/server/savegame.c	Sun May  6 01:54:40 2001
+++ modciv/server/savegame.c	Sun May  6 02:03:07 2001
@@ -433,9 +433,10 @@
 
   /* Should be handled as part of send_all_know_tiles,
      but do it here too for safety */
-  for(y=0; y<map.ysize; y++)
-    for(x=0; x<map.xsize; x++)
-      map_get_tile(x,y)->sent = 0;
+  whole_map_iterate(x, y) {
+    map_get_tile(x,y)->sent = 0;
+    remove_illegal_specials(x, y);
+  } whole_map_iterate_end;
 }
 
 /***************************************************************