It depends on where you are at in the game.I own that game so if you could describe the "ladder" then maybe your question will be answered.

It doesn't actually matter where you are in the game; the ladder will always be in the same place as long as you're still on the first quest and the ladder is called just that; It's a ladder. That's all. No other description.

The ladder is in Level 4, which is located (from your starting point):

1 screen up
2 screens left
2 screens up (Note that for the last 'up', you need the raft from Level 3 to push off the dock)

In the level, the ladder is located:

2 screens up
1 screen left
2 screens up
2 screens right; in this room, kill everything except the happy face looking sparkly creatures and then push on the left block in the center of the room; it's a passageway to the ladder.

This link:

http://db.gamefaqs.com/console/nes/..._dungeon_04.gif

Is a gif map of that level, in case you're interested.

Good luck!