In Gran Turismo 5 for the PS3, there are several Events you will unlock as you level up during the game.
Here is the list of events you will unlock in the game as you progress, and what level it requires to unlock them:
Level 1 – Gran Turismo Karting Experience
Level 2 – Jeff Gordon NASCAR School
Level 4 – Top Gear Test Track
Level 6 – AMG Driving Academy
Level 10 – Gran Turismo Rally
Level 13 – Grand Tour
Level 16 – Sebastien Loeb Rally Challenge
Level 25 – Endurance Series
Level 30 – Sebastian Vettel Challenge