Havnt thought of the cheesy name for it, someone else can help me.
How bout you start in a locked apartment. The apartment would have empty food and drinks containers scattered about and a battered radio that tells you theres a train ready to take any last survivors out of town.
So:
Level 1: Apartment is actually above a food supermarket (think a large sainsburys (or wal mart if your American)). Most of the food is gone, everythings trashed and dead bodies everywhere. You fight your way out the back entrance past the lorries to a safehouse which is in a run down shop across the street.
Level 2: From the shop, you go into the back alleys of the nearby houses, you have some free access here to go through several different paths through several different gardens but eventually a destroyed army blockade forces you to a single house, which you open and sets off the house alarm, alerting the horde. From the house you move to a safehouse situated in the house next door.
Level 3: From the house, you have to move down the main road which has ruined cars, army APCs and the like. You battle your way down this road where you are forced, due to the ruins, to a tank in which the turret is facing a large wall. You have to fire the tanks cannon, blowing up the wall but alerting the horde. After fighting the horde, you go past the wall that actually leads to a large drop, you go over the makeshift bridge into some offices where the next saferoom is.
Level 4: You fight your way through the offices to the bottom floor reception, then you have to go into a hardware store across the street where the train station is just behind it. The hardware store isnt that large as the two or three floors of offices and ICT suites are quite large. The saferoom is at the back of the hardware store.
Finale:
You go from the hardware store to the trainstation, the station has several large platforms with makeshift structres hastily built around them. There is several ruined carraiges and a walkway that runs over all the platforms. There are numerous snack houses/ticket booths with the necessary supplies. The escape train on the furthest platform has broken down and needs ten minutes to fix so you need to hold off the horde.
Good idea?