When a squad of rebels find themselves trapped under the ruins of City 17, they believed that their rescue would be a simple matter. A skirmish with an Overwatch scouting party, however, quickly escalates into a major battle amongst the debris, with great consequence.
An underground room in the first map. It is important to note that the game does not start in City 17, but rather deep in tunnels. The force of the explosion rocketed the train down the tunnel (It was sealed up at the last minute, so the train and it's passengers survived) and now all the rebels are lost inside the mineshafts, train tunnels and maintainance areas.
If the City is in ruins, isn't it a bit strange to have working electricity, lights, and machinery? I would imagine so with a Combine military presence in the area(an outpost or base that they have set up in the ruins). But that does not look the case here.
there is combine presence, theres a gate and door and a tank in the bottom right
In the description I said that the game doesn't start in the city. This is just a room in the outlands, and all the damage is recent, caused by a fight between combine soldiers and antlions.