diff --git a/src/genworld.cpp b/src/genworld.cpp
new file mode 100644
--- /dev/null
+++ b/src/genworld.cpp
@@ -0,0 +1,292 @@
+/* $Id$ */
+
+#include "stdafx.h"
+#include "openttd.h"
+#include "functions.h"
+#include "player.h"
+#include "table/sprites.h"
+#include "variables.h"
+#include "thread.h"
+#include "genworld.h"
+#include "gfx.h"
+#include "gfxinit.h"
+#include "gui.h"
+#include "network/network.h"
+#include "debug.h"
+#include "settings.h"
+#include "heightmap.h"
+#include "date.h"
+
+void GenerateLandscape(byte mode);
+void GenerateClearTile(void);
+void GenerateIndustries(void);
+void GenerateUnmovables(void);
+bool GenerateTowns(void);
+void GenerateTrees(void);
+
+void StartupEconomy(void);
+void StartupPlayers(void);
+void StartupDisasters(void);
+
+void InitializeGame(int mode, uint size_x, uint size_y);
+
+void ConvertGroundTilesIntoWaterTiles(void);
+
+/* Please only use this variable in genworld.h and genworld.c and
+ *  nowhere else. For speed improvements we need it to be global, but
+ *  in no way the meaning of it is to use it anywhere else besides
+ *  in the genworld.h and genworld.c! -- TrueLight */
+gw_info _gw;
+
+/**
+ * Set the status of the Paint flag.
+ *  If it is true, the thread will hold with any futher generating till
+ *  the drawing of the screen is done. This is handled by
+ *  SetGeneratingWorldProgress(), so calling that function will stall
+ *  from time to time.
+ */
+void SetGeneratingWorldPaintStatus(bool status)
+{
+	_gw.wait_for_draw = status;
+}
+
+/**
+ * Returns true if the thread wants the main program to do a (full) paint.
+ *  If this returns false, please do not update the screen. Because we are
+ *  writing in a thread, it can cause damaged data (reading and writing the
+ *  same tile at the same time).
+ */
+bool IsGeneratingWorldReadyForPaint(void)
+{
+	/* If we are in quit_thread mode, ignore this and always return false. This
+	 *  forces the screen to not be drawn, and the GUI not to wait for a draw. */
+	if (!_gw.active || _gw.quit_thread || !_gw.threaded) return false;
+
+	return _gw.wait_for_draw;
+}
+
+/**
+ * Tells if the world generation is done in a thread or not.
+ */
+bool IsGenerateWorldThreaded(void)
+{
+	return _gw.threaded && !_gw.quit_thread;
+}
+
+/**
+ * The internal, real, generate function.
+ */
+static void *_GenerateWorld(void *arg)
+{
+	_generating_world = true;
+	if (_network_dedicated) DEBUG(net, 0, "Generating map, please wait...");
+	/* Set the Random() seed to generation_seed so we produce the same map with the same seed */
+	if (_patches.generation_seed == GENERATE_NEW_SEED) _patches.generation_seed = _patches_newgame.generation_seed = InteractiveRandom();
+	_random_seeds[0][0] = _random_seeds[0][1] = _patches.generation_seed;
+	SetGeneratingWorldProgress(GWP_MAP_INIT, 2);
+	SetObjectToPlace(SPR_CURSOR_ZZZ, 0, 0, 0);
+
+	IncreaseGeneratingWorldProgress(GWP_MAP_INIT);
+	// Must start economy early because of the costs.
+	StartupEconomy();
+
+	// Don't generate landscape items when in the scenario editor.
+	if (_gw.mode == GW_EMPTY) {
+		SetGeneratingWorldProgress(GWP_UNMOVABLE, 1);
+
+		/* Make the map the height of the patch setting */
+		if (_game_mode != GM_MENU) FlatEmptyWorld(_patches.se_flat_world_height);
+
+		ConvertGroundTilesIntoWaterTiles();
+		IncreaseGeneratingWorldProgress(GWP_UNMOVABLE);
+	} else {
+		GenerateLandscape(_gw.mode);
+		GenerateClearTile();
+
+		// only generate towns, tree and industries in newgame mode.
+		if (_game_mode != GM_EDITOR) {
+			GenerateTowns();
+			GenerateIndustries();
+			GenerateUnmovables();
+			GenerateTrees();
+		}
+	}
+
+	// These are probably pointless when inside the scenario editor.
+	SetGeneratingWorldProgress(GWP_GAME_INIT, 3);
+	StartupPlayers();
+	IncreaseGeneratingWorldProgress(GWP_GAME_INIT);
+	StartupEngines();
+	IncreaseGeneratingWorldProgress(GWP_GAME_INIT);
+	StartupDisasters();
+	_generating_world = false;
+
+	// No need to run the tile loop in the scenario editor.
+	if (_gw.mode != GW_EMPTY) {
+		uint i;
+
+		SetGeneratingWorldProgress(GWP_RUNTILELOOP, 0x500);
+		for (i = 0; i < 0x500; i++) {
+			RunTileLoop();
+			IncreaseGeneratingWorldProgress(GWP_RUNTILELOOP);
+		}
+	}
+
+	ResetObjectToPlace();
+	SetLocalPlayer(_gw.lp);
+
+	SetGeneratingWorldProgress(GWP_GAME_START, 1);
+	/* Call any callback */
+	if (_gw.proc != NULL) _gw.proc();
+	IncreaseGeneratingWorldProgress(GWP_GAME_START);
+
+	if (_cursor.sprite == SPR_CURSOR_ZZZ) SetMouseCursor(SPR_CURSOR_MOUSE);
+	/* Show all vital windows again, because we have hidden them */
+	if (_gw.threaded && _game_mode != GM_MENU) ShowVitalWindows();
+	_gw.active   = false;
+	_gw.thread   = NULL;
+	_gw.proc     = NULL;
+	_gw.threaded = false;
+
+	DeleteWindowById(WC_GENERATE_PROGRESS_WINDOW, 0);
+	MarkWholeScreenDirty();
+
+	if (_network_dedicated) DEBUG(net, 0, "Map generated, starting game");
+
+	return NULL;
+}
+
+/**
+ * Set here the function, if any, that you want to be called when landscape
+ *  generation is done.
+ */
+void GenerateWorldSetCallback(gw_done_proc *proc)
+{
+	_gw.proc = proc;
+}
+
+/**
+ * Set here the function, if any, that you want to be called when landscape
+ *  generation is aborted.
+ */
+void GenerateWorldSetAbortCallback(gw_abort_proc *proc)
+{
+	_gw.abortp = proc;
+}
+
+/**
+ * This will wait for the thread to finish up his work. It will not continue
+ *  till the work is done.
+ */
+void WaitTillGeneratedWorld(void)
+{
+	if (_gw.thread == NULL) return;
+	_gw.quit_thread = true;
+	OTTDJoinThread(_gw.thread);
+	_gw.thread   = NULL;
+	_gw.threaded = false;
+}
+
+/**
+ * Initializes the abortion process
+ */
+void AbortGeneratingWorld(void)
+{
+	_gw.abort = true;
+}
+
+/**
+ * Is the generation being aborted?
+ */
+bool IsGeneratingWorldAborted(void)
+{
+	return _gw.abort;
+}
+
+/**
+ * Really handle the abortion, i.e. clean up some of the mess
+ */
+void HandleGeneratingWorldAbortion(void)
+{
+	/* Clean up - in SE create an empty map, otherwise, go to intro menu */
+	_switch_mode = (_game_mode == GM_EDITOR) ? SM_EDITOR : SM_MENU;
+
+	if (_gw.abortp != NULL) _gw.abortp();
+
+	if (_cursor.sprite == SPR_CURSOR_ZZZ) SetMouseCursor(SPR_CURSOR_MOUSE);
+	/* Show all vital windows again, because we have hidden them */
+	if (_gw.threaded && _game_mode != GM_MENU) ShowVitalWindows();
+	_gw.active   = false;
+	_gw.thread   = NULL;
+	_gw.proc     = NULL;
+	_gw.abortp   = NULL;
+	_gw.threaded = false;
+
+	DeleteWindowById(WC_GENERATE_PROGRESS_WINDOW, 0);
+	MarkWholeScreenDirty();
+
+	OTTDExitThread();
+}
+
+/**
+ * Generate a world.
+ * @param mode The mode of world generation (@see GenerateWorldModes).
+ * @param size_x The X-size of the map.
+ * @param size_y The Y-size of the map.
+ */
+void GenerateWorld(int mode, uint size_x, uint size_y)
+{
+	if (_gw.active) return;
+	_gw.mode   = mode;
+	_gw.size_x = size_x;
+	_gw.size_y = size_y;
+	_gw.active = true;
+	_gw.abort  = false;
+	_gw.abortp = NULL;
+	_gw.lp     = _local_player;
+	_gw.wait_for_draw = false;
+	_gw.quit_thread   = false;
+	_gw.threaded      = true;
+
+	/* This disables some commands and stuff */
+	SetLocalPlayer(PLAYER_SPECTATOR);
+	/* Make sure everything is done via OWNER_NONE */
+	_current_player = OWNER_NONE;
+
+	/* Set the date before loading sprites as some newgrfs check it */
+	SetDate(ConvertYMDToDate(_patches.starting_year, 0, 1));
+
+	/* Load the right landscape stuff */
+	GfxLoadSprites();
+	LoadStringWidthTable();
+
+	InitializeGame(IG_NONE, _gw.size_x, _gw.size_y);
+	PrepareGenerateWorldProgress();
+
+	/* Re-init the windowing system */
+	ResetWindowSystem();
+
+	/* Create toolbars */
+	SetupColorsAndInitialWindow();
+
+	if (_network_dedicated ||
+	    (_gw.thread = OTTDCreateThread(&_GenerateWorld, NULL)) == NULL) {
+		DEBUG(misc, 1, "Cannot create genworld thread, reverting to single-threaded mode");
+		_gw.threaded = false;
+		_GenerateWorld(NULL);
+		return;
+	}
+
+	/* Remove any open window */
+	DeleteAllNonVitalWindows();
+	/* Hide vital windows, because we don't allow to use them */
+	HideVitalWindows();
+
+	/* Don't show the dialog if we don't have a thread */
+	ShowGenerateWorldProgress();
+
+	/* Centre the view on the map */
+	if (FindWindowById(WC_MAIN_WINDOW, 0) != NULL) {
+		ScrollMainWindowToTile(TileXY(MapSizeX() / 2, MapSizeY() / 2));
+	}
+}