Inside is like a metro, but the stations, the path and all the construction of it, will recall a train stopping in small futuristic train station.
There are Metro card and you can top them up.
The only HUGE problem are the air conditioning system that is really HIGH, you need to cover yourself or you will get sick,
Also there is no sense at all to take the underground when the taxi are so cheap and they will bring you in front of the place were you want to go.
Except fot that could be usefull to have a real underground system and not a big train in the middle of the buildings.
PS if you want to go to the mall, yes is true there is the stop, but then you need to go by foot for 15 minutes inside tunnels.... no comment.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.