In a large soup pot, heat olive oil over medium-high heat.
Add onion, leeks, carrots, and garlic, season with salt, and cook about 7-10 minutes, until the vegetables begin to soften.
Add vegetable broth and bring to a boil.
Reduce heat to medium-low and let simmer for 20 minutes.
Puree with an immersion blender or in a blender.