The oldest part of Earth's crust is found in continental shields, which are large, stable areas of very ancient, crystalline rock. These areas are typically found in the interiors of continents and have been relatively undisturbed for billions of years.

The Canadian Shield, located in North America, is a prime example of a continental shield. It is estimated to be around 4 billion years old, making it one of the oldest parts of Earth's crust.

While there are some smaller, older fragments of crust found elsewhere, the vast majority of the Earth's oldest crust is located within these continental shields.