Ok, let's see:
2 new automobile roads that will last for another ten years at least (including 35 tunnels and bridges)
1 railroad line
2 gas pipelines
1 power plant + 17 substations to provide energy
43 hotels (20K+ guests)
1 Stadium
1 Skiing center
1 Skating center
Well, it's a total waste of money!
Now, about these $50bn. The real figure is only about $6bn (I mean the money spent directly on the Olympics, not the infrastructure that will last for the next few decades).