diff -Nur -Xfreeciv/diff_ignore freeciv/common/tech.c freeciv-change/common/tech.c
--- freeciv/common/tech.c	Thu Aug 23 20:24:59 2001
+++ freeciv-change/common/tech.c	Sat Aug 25 01:25:54 2001
@@ -27,7 +27,7 @@
    client/packhand.c (for the client) */
 
 static const char *flag_names[] = {
-  "Bonus_Tech","Boat_Fast","Bridge","Railroad","Fortress",
+  "Bonus_Tech","Boat_Fast","Bridge","Railroad","Fortress","Watchtower",
   "Population_Pollution_Inc","Trade_Revenue_Reduce","Airbase","Farmland",
   "Reduce_Trireme_Loss1", "Reduce_Trireme_Loss2"
 };
diff -Nur -Xfreeciv/diff_ignore freeciv/common/tech.h freeciv-change/common/tech.h
--- freeciv/common/tech.h	Thu Aug 23 20:24:59 2001
+++ freeciv-change/common/tech.h	Sat Aug 25 01:43:08 2001
@@ -46,6 +46,7 @@
   TF_BRIDGE,    /* "Settler" unit types can build bridges over rivers */
   TF_RAILROAD,  /* "Settler" unit types can build rail roads */
   TF_FORTRESS,  /* "Settler" unit types can build fortress */
+  TF_WATCHTOWER, /* Units get enhanced visionrange in a fortress (=fortress acts also as a watchtower) */
   TF_POPULATION_POLLUTION_INC,  /* Increase the pollution factor created by popultaion by one */
   TF_TRADE_REVENUE_REDUCE, /* When known by the player establishing a trade route 
                               reduces the initial revenue by cumulative factors of 2/3 */
diff -Nur -Xfreeciv/diff_ignore freeciv/data/default/techs.ruleset freeciv-change/data/default/techs.ruleset
--- freeciv/data/default/techs.ruleset	Fri Mar 30 01:08:39 2001
+++ freeciv-change/data/default/techs.ruleset	Sat Aug 25 01:25:13 2001
@@ -38,6 +38,7 @@
 ; "Railroad" = "Settler" unit types can build rail roads
 ; "Farmland" = "Settler" unit types can build farmland
 ; "Fortress" = "Settler" unit types can build fortress
+; "Watchtower" = Units get enhanced visionrange in a fortress
 ; "Population_Pollution_Inc" = Increase the pollution factor created by
 ;                              popultaion by one
 ; "Trade_Revenue_Reduce" = When known by the player establishing a trade
@@ -271,7 +272,7 @@
 name     = _("Invention")
 req1     = "Engineering"
 req2     = "Literacy"
-flags    = ""
+flags    = "Watchtower"
 
 [advance_iron_working]
 name     = _("Iron Working")
diff -Nur -Xfreeciv/diff_ignore freeciv/server/citytools.c freeciv-change/server/citytools.c
--- freeciv/server/citytools.c	Fri Aug 24 10:22:07 2001
+++ freeciv-change/server/citytools.c	Mon Aug 27 04:51:29 2001
@@ -897,8 +897,18 @@
   city_refresh(pcity);
 
   city_incite_cost(pcity);
+  /* Put vision back to normal, if fortress acted as a watchtower */
+  if (player_knows_techs_with_flag(pplayer, TF_WATCHTOWER)
+      && map_get_tile(x,y)->special & S_FORTRESS)
+  {
+     unit_list_iterate (map_get_tile(x,y)->units, punit)
+       unfog_area(pplayer, punit->x, punit->y, get_unit_type(punit->type)->vision_range);
+       fog_area(pplayer, punit->x, punit->y, get_watchtower_vision(punit));
+     unit_list_iterate_end;
+  }
   map_clear_special(x, y, S_FORTRESS);
   send_tile_info(NULL, x, y);
+
   initialize_infrastructure_cache(pcity);
   reset_move_costs(x, y);
 /* I stupidly thought that setting S_ROAD took care of this, but of course
diff -Nur -Xfreeciv/diff_ignore freeciv/server/maphand.c freeciv-change/server/maphand.c
--- freeciv/server/maphand.c	Fri Aug 24 10:22:10 2001
+++ freeciv-change/server/maphand.c	Mon Aug 27 05:55:27 2001
@@ -686,7 +686,11 @@
   freelog(LOG_DEBUG, "Removing unit sight points at  %i,%i", punit->x,
 	  punit->y);
 
-  fog_area(pplayer, x, y, range);
+  if (map_get_special(punit->x, punit->y) & S_FORTRESS
+      && unit_profits_of_watchtower(punit))
+    fog_area(pplayer, x, y, get_watchtower_vision(punit));
+  else
+    fog_area(pplayer, x, y, range);
 }
 
 /**************************************************************************
diff -Nur -Xfreeciv/diff_ignore freeciv/server/plrhand.c freeciv-change/server/plrhand.c
--- freeciv/server/plrhand.c	Sat Jul 21 19:45:36 2001
+++ freeciv-change/server/plrhand.c	Mon Aug 27 05:02:12 2001
@@ -259,6 +259,21 @@
     upgrade_city_rails(plr, was_discovery);
   }
 
+  /* enhace vision of units inside a fortress */
+  if (tech_flag(tech_found,TF_WATCHTOWER))
+  {
+    unit_list_iterate(plr->units, punit)
+    {
+      if (map_get_tile(punit->x, punit->y)->special & S_FORTRESS
+	  && is_ground_unit(punit))
+      {
+        unfog_area(plr, punit->x, punit->y, get_watchtower_vision(punit));
+        fog_area(plr, punit->x, punit->y, get_unit_type(punit->type)->vision_range);
+      }
+    }
+     unit_list_iterate_end;
+  }
+
   if (tech_found==plr->ai.tech_goal)
     plr->ai.tech_goal=A_NONE;
 
diff -Nur -Xfreeciv/diff_ignore freeciv/server/savegame.c freeciv-change/server/savegame.c
--- freeciv/server/savegame.c	Fri Aug 24 10:22:10 2001
+++ freeciv-change/server/savegame.c	Mon Aug 27 05:57:53 2001
@@ -43,6 +43,7 @@
 #include "ruleset.h"
 #include "spacerace.h"
 #include "srv_main.h"
+#include "unittools.h"
 
 #include "aicity.h"
 #include "aiunit.h"
@@ -1123,7 +1124,14 @@
       } square_iterate_end;
     }
     /* allocate the unit's contribution to fog of war */
-    unfog_area(unit_owner(punit), punit->x, punit->y,
+    if (unit_profits_of_watchtower(punit)
+        && map_get_special(punit->x, punit->y) & S_FORTRESS)
+    {
+      unfog_area(unit_owner(punit), punit->x, punit->y,
+	       get_watchtower_vision(punit));
+    }
+    else
+      unfog_area(unit_owner(punit), punit->x, punit->y,
 	       get_unit_type(punit->type)->vision_range);
 
     unit_list_insert_back(&plr->units, punit);
diff -Nur -Xfreeciv/diff_ignore freeciv/server/unittools.c freeciv-change/server/unittools.c
--- freeciv/server/unittools.c	Fri Aug 24 10:22:12 2001
+++ freeciv-change/server/unittools.c	Mon Aug 27 05:30:39 2001
@@ -822,6 +822,20 @@
 	  send_tile_info(0, punit->x, punit->y);
 	  set_unit_activity(punit, ACTIVITY_IDLE);
 	}
+
+	/* If a watchtower has been pillaged, reduce sight to normal */
+        if (what == S_FORTRESS
+  	   && player_knows_techs_with_flag(pplayer, TF_WATCHTOWER))
+        {
+          freelog(LOG_VERBOSE, "Watchtower pillaged!");
+          unit_list_iterate (map_get_tile(punit->x, punit->y)->units, punit2)
+	    if (is_ground_unit(punit2))
+	    {	    
+              unfog_area(pplayer, punit2->x, punit2->y, get_unit_type(punit2->type)->vision_range);	  
+              fog_area(pplayer, punit2->x, punit2->y, get_watchtower_vision(punit2));
+	    }
+          unit_list_iterate_end;
+        }
       }
     }
     else if (total_activity_targeted (punit->x, punit->y,
@@ -836,7 +850,21 @@
 	}
       unit_list_iterate_end;
       send_tile_info(NULL, punit->x, punit->y);
-    }
+      
+      /* If a watchtower has been pillaged, reduce sight to normal */
+      if (what_pillaged == S_FORTRESS
+          && player_knows_techs_with_flag(pplayer, TF_WATCHTOWER))
+      {
+        freelog(LOG_VERBOSE, "Watchtower(2) pillaged!");
+        unit_list_iterate (map_get_tile(punit->x, punit->y)->units, punit2)
+          if (is_ground_unit(punit2))
+          {
+            unfog_area(pplayer, punit2->x, punit2->y, get_unit_type(punit2->type)->vision_range);
+            fog_area(pplayer, punit2->x, punit2->y, get_watchtower_vision(punit2));
+          }
+        unit_list_iterate_end;
+      }
+    }    
   }
 
   if (activity==ACTIVITY_POLLUTION) {
@@ -860,6 +888,18 @@
 	>= map_build_fortress_time(punit->x, punit->y)) {
       map_set_special(punit->x, punit->y, S_FORTRESS);
       unit_activity_done = 1;
+      /* watchtower becomes effective */
+      if (player_knows_techs_with_flag(pplayer, TF_WATCHTOWER))
+      {      
+        unit_list_iterate(ptile->units, punit) 
+	{
+	  if (is_ground_unit(punit))
+	  {
+            fog_area(pplayer, punit->x, punit->y, get_unit_type(punit->type)->vision_range);
+            unfog_area(pplayer, punit->x, punit->y, get_watchtower_vision(punit));
+	  }
+        } unit_list_iterate_end; 
+      }
     }
   }
 
@@ -1538,8 +1578,18 @@
 
   conn_list_do_buffer(&pplayer->connections);
   punit->type = to_unit;
-  unfog_area(pplayer,punit->x,punit->y, get_unit_type(to_unit)->vision_range);
+
+  if (map_get_tile(punit->x, punit->y)->special & S_FORTRESS
+      && unit_profits_of_watchtower(punit))
+  {
+    unfog_area(pplayer, punit->x, punit->y, get_watchtower_vision(punit));
+  }
+  else
+  {
+    unfog_area(pplayer,punit->x,punit->y, get_unit_type(to_unit)->vision_range);
+  }
   fog_area(pplayer,punit->x,punit->y,range);
+
   send_unit_info(0, punit);
   conn_list_do_unbuffer(&pplayer->connections);
 }
@@ -1642,7 +1692,12 @@
   punit->transported_by = -1;
   punit->pgr = NULL;
 
-  unfog_area(pplayer,x,y,get_unit_type(punit->type)->vision_range);
+
+  if (map_get_tile(x, y)->special & S_FORTRESS
+      && unit_profits_of_watchtower(punit))
+    unfog_area(pplayer, punit->x, punit->y, get_watchtower_vision(punit));
+  else
+    unfog_area(pplayer, x, y, get_unit_type(punit->type)->vision_range);
   send_unit_info(0, punit);
   maybe_make_first_contact(x, y, punit->owner);
   wakeup_neighbor_sentries(punit);
@@ -2892,7 +2947,15 @@
      and then fog the old territory. This means that the player gets a chance to
      see the newly explored territory while the client moves the unit, and both
      areas are visible during the move */
-  unfog_area(pplayer, dest_x, dest_y, get_unit_type(punit->type)->vision_range);
+  /* Enhace vision if unit steps into a fortress, only if its a
+     groundunit */
+  if (unit_profits_of_watchtower(punit)
+      && pdesttile->special & S_FORTRESS)
+  {
+    unfog_area(pplayer, dest_x, dest_y, get_watchtower_vision(punit));
+  }
+  else
+    unfog_area(pplayer, dest_x, dest_y, get_unit_type(punit->type)->vision_range);
 
   unit_list_unlink(&psrctile->units, punit);
   punit->x = dest_x;
@@ -2915,7 +2978,11 @@
     set_unit_activity(punit, ACTIVITY_SENTRY);
   }
   send_unit_info_to_onlookers(0, punit, src_x, src_y, 0, 0);
-  fog_area(pplayer, src_x, src_y, get_unit_type(punit->type)->vision_range);
+  if (unit_profits_of_watchtower(punit) 
+      && psrctile->special & S_FORTRESS)
+    fog_area(pplayer, src_x, src_y, get_watchtower_vision(punit));
+  else
+    fog_area(pplayer, src_x, src_y, get_unit_type(punit->type)->vision_range);
 
   handle_unit_move_consequences(punit, src_x, src_y, dest_x, dest_y);
 
@@ -3077,4 +3144,28 @@
 		     unit_types[punit->type].name);
   }
   return 0;
+}
+
+/**************************************************************************
+...
+**************************************************************************/
+int get_watchtower_vision(struct unit *punit)
+{
+  int watchtower_vision=2;
+  int watchtower_extra_vision=0;
+  int base_vision=get_unit_type(punit->type)->vision_range;
+
+  return MAX(base_vision,
+            MAX(watchtower_vision, base_vision+watchtower_extra_vision));
+}
+
+/**************************************************************************
+...
+**************************************************************************/
+int unit_profits_of_watchtower(struct unit *punit)
+{
+  int playerid = punit->owner;
+  struct player *pplayer = get_player(playerid);
+  return (is_ground_unit(punit)
+          && player_knows_techs_with_flag(pplayer, TF_WATCHTOWER));
 }
diff -Nur -Xfreeciv/diff_ignore freeciv/server/unittools.h freeciv-change/server/unittools.h
--- freeciv/server/unittools.h	Mon Aug 13 14:25:30 2001
+++ freeciv-change/server/unittools.h	Sun Aug 26 16:57:42 2001
@@ -45,6 +45,8 @@
 int teleport_unit_to_city(struct unit *punit, struct city *pcity, int move_cost,
 			  int verbose);
 void resolve_unit_stack(int x, int y, int verbose);
+int get_watchtower_vision(struct unit *punit);
+int unit_profits_of_watchtower(struct unit *punit);
 
 
 /* creation/deletion/upgrading */