Here's my attempt at a map. Does it look about right?
A B C D E F G H I J K L M N O P Q R S T
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
1 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
3 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
5 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
6 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
7 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
8 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
9 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
10 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
11 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
12 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
13 | | | | | | | | | | | | | | | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
14 | | | | | | | | | |###|--DDD--|###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
15 | | | | | | | | | |###| | |###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
16 | | | | | | | | | |###| | |###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
17 | | | | | | | | | |###| | |###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
18 | | | | | |###| V |###|###|###| | |###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
19 | | | | |###| | | | | | |###| | | | | | | |
+ N +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
20 | ^ | | | |###| H | | | | | |###| | | | | | | |
+ | +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
| | | | |###| $ |###|###|###|###|###|###| | | | | | | |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
^
|
ENTRY
### = Wall of corridor
H = Dead hobgoblin
--DDD-- = Door
V = Crossbow trap
$ = Secret door
Scale 1 square = 5ft