- Just download that, unrar it and stick it in Steam\steamapps\common\left 4 dead\left4dead\maps
- Then fire up L4D, pull up the console and type map l4d_vs_hunter_city_b3
- That should load it, ignore the error and press M to switch to the infected
- Now, if you're not a hunter pull up the console again and type kill until you're a hunter.
- Try to get to the end without cheating