C++11 Multidimentional Array Iteration

To iterate through a C style multidimentional array we have

int arr[3][4];

for (int row = 0; row < 3; row++){
    for (int col = 0; col < 4; col++){
        ...
    }
}

But how may one use iterators to iterate over the following:

array<array<int, 4>, 3> arr;

Using the following iterators?

array<array<int, 4>, 3>::iterator it1;

array<int, 4>::iterator it2;