Okay buddy, let me explain to you what Alexandria on the Indus is. A long long time ago, when people used to travel from one place to another, there was a wise king named Alexander the Great. He wanted to conquer new lands and spread his empire far and wide. So he and his army traveled all the way to a place called the Indus Valley, which is now part of modern-day Pakistan.
Now, Alexander was a smart king, and he wanted to make sure his people who were traveling with him had a place to stay, eat, and rest. So he decided to build a city in this area. This city was named after him, and it was called "Alexandria on the Indus."
It was a very important city because it was located at the point where the Indus river meets the sea, so it became a hub for trade and commerce. People from all around the region would come to Alexandria on the Indus to buy and sell goods. The city also had a big port, which made it easy for ships to come and go with their cargo.
The city had many important buildings, like a palace for the king, a temple for the gods, and a market for people to buy and sell things. Alexander wanted this city to be a symbol of his power and influence in the region, so he made sure to build it to be very grand and impressive.
Eventually, Alexander left the city and it fell into disrepair, but for a long time, it was an important hub for trade and commerce in the region. And that is the story of Alexandria on the Indus, my little buddy!