diff --git a/dat/knox.des b/dat/knox.des
index bf602c1ed..48cef7414 100644
--- a/dat/knox.des
+++ b/dat/knox.des
@@ -6,6 +6,8 @@
 MAZE:"knox",' '
 FLAGS: noteleport
 GEOMETRY:center,center
+# Fort's entry is via a secret door rather than a drawbridge;
+# the moat must be manually circumvented.
 MAP
 ----------------------------------------------------------------------------
 | |........|...............................................................|
@@ -37,11 +39,27 @@ TELEPORT_REGION:(06,16,09,17),(0,0,0,0),up
 TELEPORT_REGION:(06,16,09,17),(0,0,0,0),down
 #   Throne room, with Croesus on the throne
 REGION:(37,08,46,11),lit,"throne"
-MONSTER:('@',"Croesus"),(43,10),hostile
+#   50% chance each to move throne and/or fort's entry secret door up one row
+IF [50%] {
+   MONSTER:('@',"Croesus"),(43,10),hostile
+} ELSE {
+   MONSTER:('@',"Croesus"),(43,09),hostile
+   TERRAIN:(43,09), '\'
+   TERRAIN:(43,10), '.'
+}
+IF [50%] {
+   TERRAIN:(47,09), 'S'
+   TERRAIN:(47,10), '|'
+}
 #   The Vault
 #   Using unfilled morgue for
 #   identification in mkmaze.c
 REGION:(21,08,35,11),lit,"morgue",unfilled
+#   Vault entrance also varies
+IF [50%] {
+   TERRAIN:(36,09), '|'
+   TERRAIN:(36,10), 'S'
+}
 #   Corner towers
 REGION:(19,06,21,06),lit,"ordinary"
 REGION:(46,06,48,06),lit,"ordinary"
diff --git a/doc/fixes36.1 b/doc/fixes36.1
index af6dc5210..d59419478 100644
--- a/doc/fixes36.1
+++ b/doc/fixes36.1
@@ -216,6 +216,8 @@ for menustyles traditional or combination, 'A' (or object ID) followed by i
 exploding chest trap would destroy uchain while still worn if uball carried
 if monster shapechange message "<foo> turns into <bar>!" was given, <bar>
 	could be "it" (if <foo> sensed telepathically and <bar> is mindless)
+automatic annotation for Ft.Ludios level got applied when a drawbridge became
+	mapped, but entry there is a secret door rather than a drawbridge
 
 post-3.6.0: fix "object lost" panic during pickup caused by sortloot revamp
 post-3.6.0: more sortloot revisions
diff --git a/src/dungeon.c b/src/dungeon.c
index 82610573a..0d2c93466 100644
--- a/src/dungeon.c
+++ b/src/dungeon.c
@@ -2465,6 +2465,9 @@ recalc_mapseen()
             /*  An automatic annotation is added to the Castle and
              *  to Fort Ludios once their structure's main entrance
              *  has been seen (in person or via magic mapping).
+             *  For the Fort, that entrance is just a secret door
+             *  which will be converted into a regular one when
+             *  located (or destroyed).
              * DOOR: possibly a lowered drawbridge's open portcullis;
              * DBWALL: a raised drawbridge's "closed door";
              * DRAWBRIDGE_DOWN: the span provided by lowered bridge,
@@ -2474,6 +2477,26 @@ recalc_mapseen()
              *  the adjacent DBWALL has been seen.
              */
             case DOOR:
+                if (Is_knox(&u.uz)) {
+                    int ty, tx = x - 4;
+
+                    /* Throne is four columns left, either directly in
+                     * line or one row higher or lower, and doesn't have
+                     * to have been seen yet.
+                     *   ......|}}}.
+                     *   ..\...S}...
+                     *   ..\...S}...
+                     *   ......|}}}.
+                     * For 3.6.0 and earlier, it was always in direct line:
+                     * both throne and door on the lower of the two rows.
+                     */
+                    for (ty = y - 1; ty <= y + 1; ++ty)
+                        if (isok(tx, ty) && IS_THRONE(levl[tx][ty].typ)) {
+                            mptr->flags.ludios = 1;
+                            break;
+                        }
+                    break;
+                }
                 if (is_drawbridge_wall(x, y) < 0)
                     break;
             /* else FALLTHRU */
@@ -2481,8 +2504,6 @@ recalc_mapseen()
             case DRAWBRIDGE_DOWN:
                 if (Is_stronghold(&u.uz))
                     mptr->flags.castle = 1, mptr->flags.castletune = 1;
-                else if (Is_knox(&u.uz))
-                    mptr->flags.ludios = 1;
                 break;
             default:
                 break;