Implementations of the standard library are great places to search for idiomatic and performant C++ code. For instance, if you want to read some really interesting template code, you should give std::chrono a shot, as it demonstrates some useful techniques and has a fresh approach to this. A link to libstdc++'s implementation can be found in the Further reading section.
When it comes to other places of the library, even a quick peek at its containers shows that their interfaces tend to differ from their counterparts in other programming languages. To show this, let's take a look at a pretty straightforward class from the standard library, std::array, and analyze it bit by bit:
template <class T, size_t N>
struct array {
// types:
typedef T& reference;
typedef const T& const_reference;
typedef /*implementation-defined*/ iterator;
typedef /*implementation-defined*/ const_iterator;
typedef size_t size_type;
typedef ptrdiff_t...