Wonder Boy in Monster Land/Round 11

Proceed to the right. At the end of the first region, jump into the water to go down. Take the underground river to the right and enter the cave.

From the cave, jump into the fake lava at the right part of the area. About five screens down, where you see the second single platform on the right, you can collect a hidden bag of gold in the alcove that is down and to the left. Continue downward and to the right to reach the next section.

A hidden armor shop is to the right of the first door.

The white knight is located behind the third door, and he has the key to the final round.