Harrisburg is the capital of the state of Pennsylvania in the United States of America. The population of Harrisburg is around 650,000.
Icebergs are huge chunks of ice that break off from the ice collected around land, or from glaciers that reach the sea. They float, but most of them is underwater and you can't see it, which has coined the phrase "tip of the iceberg" meaning that you can only see a small part of something and the problem is actually a lot bigger than it seems.
Johannesburg is the largest city in South Africa. It has a population of around 3.9 million.
The Grand Duchy of Luxembourg is a country in western Europe. The capital of Luxembourg is the city of Luxembourg, which has a population of around 94,000. People in Luxembourg speak Luxembourgish, French and German.