Okay kiddo, imagine there's a big line on a map and it's very important because it helps to protect a country. This line is called the Metaxas Line. It's like a big fence that goes all the way along the border of Greece and Bulgaria.
Now, why does Greece need this big fence? Well, a long time ago, there was a big war and Greece was worried that Bulgaria might try to invade them again. So, they built this big fence to make it harder for Bulgaria's army to get into Greece.
The Metaxas Line is not just a regular fence though. It's very strong and has lots of big, heavy blocks of concrete called bunkers. These bunkers have tiny little windows for people to shoot out of and protect the border.
So, the Metaxas Line is like a big fence with bunkers to protect Greece from invaders. It's like a big shield to keep people safe.