The Indus Valley people were brilliant city planners. Their streets were laid out in neat grids, like a modern town. Each house had its own bathroom with a clay pipe carrying water away into a covered drain under the street. That is something most cities in Europe didn't have until thousands of years later.
They built everything out of bricks - millions and millions of bricks, all the same size. Each brick is exactly 1 unit wide, 2 units long, and half a unit thick. The bricks were so well made that you can still see the walls standing today, baked hard by the sun for fifty centuries.
Archaeologists have dug up beautiful things from these cities: tiny clay toys with wheels (so children played with toy carts even then), jewellery made of shells, board games with playing pieces, and little stone seals carved with pictures of animals. We have not yet worked out how to read their writing - it is one of the world's great unsolved puzzles.
Mohenjo-daro had a great public swimming pool right in the middle of the city, called the Great Bath. It was made of brick and lined with a special kind of waterproof plaster. Imagine a town centre with a public pool 4,500 years ago - they invented the modern lido before anyone else.