Underground city

Okay kiddo, imagine if you had a secret place to play hide and seek with your friends where the sun couldn't reach you. That's just like an underground city, but for adults.

Cities like Toronto, Montreal, and Beijing have underground cities. They are tunnels and rooms built underneath the regular city streets, just like a secret underground playground.

Now mom, dad, and the big people who work there can go shopping, eat, work out, and even go to the movies down there, all without having to step outside into the cold or rain.

It's like a secret, indoor city below the real city, and it helps people stay warm or cool and dry, no matter what the weather is like outside.