diff --git a/asm/field_region_map.s b/asm/field_region_map.s
index dd9a9e432c..2428f2984b 100644
--- a/asm/field_region_map.s
+++ b/asm/field_region_map.s
@@ -5,44 +5,4 @@
 
 	.text
 
-	thumb_func_start sub_8170428
-sub_8170428: @ 8170428
-	push {r4,lr}
-	sub sp, 0xC
-	ldr r4, =gUnknown_0203BCD0
-	ldr r0, [r4]
-	ldrb r0, [r0, 0xA]
-	cmp r0, 0
-	beq _08170460
-	movs r0, 0
-	movs r1, 0x11
-	bl FillWindowPixelBuffer
-	ldr r2, [r4]
-	adds r2, 0xC
-	movs r0, 0x1
-	str r0, [sp]
-	movs r0, 0
-	str r0, [sp, 0x4]
-	str r0, [sp, 0x8]
-	movs r1, 0x1
-	movs r3, 0
-	bl PrintTextOnWindow
-	movs r0, 0
-	bl schedule_bg_copy_tilemap_to_vram
-	b _08170470
-	.pool
-_08170460:
-	movs r0, 0
-	movs r1, 0x11
-	bl FillWindowPixelBuffer
-	movs r0, 0
-	movs r1, 0x3
-	bl CopyWindowToVram
-_08170470:
-	add sp, 0xC
-	pop {r4}
-	pop {r0}
-	bx r0
-	thumb_func_end sub_8170428
-
 	.align 2, 0 @ Don't pad with nop.
diff --git a/include/region_map.h b/include/region_map.h
index 5eeb3a95f7..20756404cf 100644
--- a/include/region_map.h
+++ b/include/region_map.h
@@ -219,11 +219,66 @@ enum {
     MAPSEC_TRAINER_HILL
 };
 
+struct RegionMap {
+    u8 unk_00;
+    u8 unk_01;
+    bool8 unk_02;
+    u8 unk_03;
+    u8 mapSecName[0x14];
+    u16 mapSecId;
+    u8 unk16;
+    u8 everGrandeCityArea;
+    u8 (*inputCallback)(void);
+    struct Sprite *cursorSprite;
+    struct Sprite *playerIconSprite;
+    s32 bg2x;
+    s32 bg2y;
+    u32 unk2C;  //
+    u32 unk30;  //  Map rotation parameters
+    u32 unk34;  //  Likely a scrapped feature
+    u32 unk38;  //
+    s32 unk3C;
+    s32 unk40;
+    s32 unk44;
+    s32 unk48;
+    s32 unk4C;
+    s32 unk50;
+    u16 cursorPosX;
+    u16 cursorPosY;
+    u16 cursorTileTag;
+    u16 cursorPaletteTag;
+    s16 scrollX;
+    s16 scrollY;
+    s16 unk60;
+    s16 unk62;
+    u16 unk64;
+    u16 unk66;
+    u16 unk68;
+    u16 unk6A;
+    u16 unk6C;
+    u16 unk6E;
+    u16 playerIconTileTag;
+    u16 playerIconPaletteTag;
+    u16 unk74;
+    u16 unk76;
+    bool8 zoomed;
+    u8 initStep;
+    s8 unk7A;
+    s8 cursorDeltaX;
+    s8 cursorDeltaY;
+    bool8 needUpdateVideoRegs;
+    bool8 blinkPlayerIcon;
+    bool8 playerIsInCave;
+    /*0x084*/ u8 filler80[0x100];
+    /*0x184*/ u8 cursorSmallImage[0x100];
+    /*0x284*/ u8 cursorLargeImage[0x600];
+}; // size = 0x884
+
 // Exported RAM declarations
 
 // Exported ROM declarations
 void GetMapName(u8 *, u16, u16);
-void sub_8122CDC(void *data, u8 argument);
+void sub_8122CDC(struct RegionMap *regionMap, u8 argument);
 void sub_8124288(u16 x, u16 y);
 void sub_81240D4(u16 x, u16 y);
 u8 sub_81230AC(void);
diff --git a/src/field_region_map.c b/src/field_region_map.c
index 399ae90701..f782680189 100644
--- a/src/field_region_map.c
+++ b/src/field_region_map.c
@@ -20,8 +20,8 @@
 
 EWRAM_DATA struct {
     MainCallback callback;
-    u8 filler_004[0x4];
-    u8 filler_008[0x884];
+    u32 filler_004;
+    struct RegionMap regionMap;
     u16 state;
 } *gUnknown_0203BCD0 = NULL;
 
@@ -31,7 +31,7 @@ static void sub_81701C4(void);
 static void sub_8170260(void);
 static void sub_8170274(void);
 static void sub_8170290(void);
-void sub_8170428(void);
+static void sub_8170428(void);
 
 // .rodata
 
@@ -95,7 +95,7 @@ void sub_8170290(void)
     switch (gUnknown_0203BCD0->state)
     {
         case 0:
-            sub_8122CDC(gUnknown_0203BCD0->filler_008, 0);
+            sub_8122CDC(&gUnknown_0203BCD0->regionMap, 0);
             sub_8124288(0, 0);
             sub_81240D4(1, 1);
             gUnknown_0203BCD0->state ++;
@@ -103,7 +103,7 @@ void sub_8170290(void)
         case 1:
             SetWindowBorderStyle(1, 0, 0x27, 0xd);
             offset = GetStringCenterAlignXOffset(1, gText_Hoenn, 0x38);
-            PrintTextOnWindow(1, 1, gText_Hoenn, offset, 1, 0, 0);
+            PrintTextOnWindow(1, 1, gText_Hoenn, offset, 1, 0, NULL);
             schedule_bg_copy_tilemap_to_vram(0);
             SetWindowBorderStyle(0, 0, 0x27, 0xd);
             sub_8170428();
@@ -153,3 +153,18 @@ void sub_8170290(void)
             break;
     }
 }
+
+static void sub_8170428(void)
+{
+    if (gUnknown_0203BCD0->regionMap.unk_02)
+    {
+        FillWindowPixelBuffer(0, 0x11);
+        PrintTextOnWindow(0, 1, gUnknown_0203BCD0->regionMap.mapSecName, 0, 1, 0, NULL);
+        schedule_bg_copy_tilemap_to_vram(0);
+    }
+    else
+    {
+        FillWindowPixelBuffer(0, 0x11);
+        CopyWindowToVram(0, 3);
+    }
+}