The Forum Shops is a truly massive mall in the center of the strip. You can access it through Caesars' casino or from the outside where there are entrances adjacent to Caesars and I believe also from their parking garage. You can cross from the other side of the strip near the Venetian to get to it.
At last count, the mall has over 160 stores and 13 restaurants. There's also a huge fish tank in one end of the mall that has an hourly light show, and twice daily feedings that are worth seeing.
If you visit the Hugo Boss store, ask for Damian or Lamont; great guys.