Wonder Boy in Monster World/Purapril, the Aqua Capital

Purapril: The Aqua Capital
After falling in the gap (mind the gold in the grass left from the ladder) enter the door, walk to the next door and enter it again.

You are now in the underground passage of Purapril castle. Walk to the left, after a while you'll encounter a knight. He can be easily defeated by striking with your sword on his feet. After you've defeated him Princess Sheila Purapril will thank you and ask you to come to her kingdom.

Climb the tower to reach it. Once there, make sure to talk to everyone, they have valuable information for you. When you're done, leave the kingdom. Go to the bottom of the tower and enter the door, which was closed before. You're now in Purapril the Aqua capital. This is an important town in the game, you have to return here often. Buy some goods and leave the village through the south-west exit.