diff --git a/include/cppast/cpp_entity.hpp b/include/cppast/cpp_entity.hpp
index 049a6bc..47b5fa0 100644
--- a/include/cppast/cpp_entity.hpp
+++ b/include/cppast/cpp_entity.hpp
@@ -36,15 +36,20 @@ namespace cppast
         }
 
         /// \returns A [ts::optional_ref]() to the parent entity in the AST.
-        type_safe::optional_ref<cpp_entity> parent() const noexcept
+        type_safe::optional_ref<const cpp_entity> parent() const noexcept
         {
             return parent_;
         }
 
     protected:
         /// \effects Creates it giving it the parent entity and the name.
-        cpp_entity(type_safe::optional_ref<cpp_entity> parent, std::string name)
-        : parent_(std::move(parent)), name_(std::move(name))
+        cpp_entity(const cpp_entity& parent, std::string name)
+        : parent_(parent), name_(std::move(name))
+        {
+        }
+
+        /// \effects Creates it giving it no parent and the name.
+        cpp_entity(std::nullptr_t, std::string name) : name_(std::move(name))
         {
         }
 
@@ -52,10 +57,11 @@ namespace cppast
         /// \returns The type of the entity.
         virtual cpp_entity_type do_get_entity_type() const noexcept = 0;
 
-        type_safe::optional_ref<cpp_entity> parent_;
-        std::string                         name_;
+        type_safe::optional_ref<const cpp_entity> parent_;
+        std::string                               name_;
 
-        friend detail::intrusive_list<cpp_entity>;
+        template <typename T>
+        friend struct detail::intrusive_list_access;
     };
 } // namespace cppast
 
diff --git a/include/cppast/cpp_entity_type.hpp b/include/cppast/cpp_entity_type.hpp
index 8f1efe4..838624c 100644
--- a/include/cppast/cpp_entity_type.hpp
+++ b/include/cppast/cpp_entity_type.hpp
@@ -11,6 +11,8 @@ namespace cppast
     enum class cpp_entity_type
     {
         file_t,
+
+        namespace_t,
     };
 
     /// \returns Whether or not a given entity type is one derived from [cppast::cpp_scope]().
diff --git a/include/cppast/cpp_file.hpp b/include/cppast/cpp_file.hpp
index 6c78dd4..c809a1f 100644
--- a/include/cppast/cpp_file.hpp
+++ b/include/cppast/cpp_file.hpp
@@ -9,7 +9,7 @@
 
 namespace cppast
 {
-    /// A [cppast::cpp_entity]() referring to a file.
+    /// A [cppast::cpp_entity]() modelling a file.
     ///
     /// This is the top-level entity of the AST.
     class cpp_file final : public cpp_entity
@@ -36,6 +36,12 @@ namespace cppast
                 return std::move(file_);
             }
 
+            /// \returns A reference to (not yet finished) file.
+            const cpp_file& get() const noexcept
+            {
+                return *file_;
+            }
+
         private:
             std::unique_ptr<cpp_file> file_;
         };
diff --git a/include/cppast/cpp_namespace.hpp b/include/cppast/cpp_namespace.hpp
new file mode 100644
index 0000000..54f7b49
--- /dev/null
+++ b/include/cppast/cpp_namespace.hpp
@@ -0,0 +1,66 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#ifndef CPPAST_CPP_NAMESPACE_HPP_INCLUDED
+#define CPPAST_CPP_NAMESPACE_HPP_INCLUDED
+
+#include <cppast/cpp_scope.hpp>
+
+namespace cppast
+{
+    /// A [cppast::cpp_entity]() modelling a namespace.
+    class cpp_namespace : public cpp_scope
+    {
+    public:
+        /// Builds a [cppast::cpp_namespace]().
+        class builder
+        {
+        public:
+            /// \effects Sets the namespace name and whether it is inline.
+            explicit builder(const cpp_entity& parent, std::string name, bool is_inline)
+            : namespace_(new cpp_namespace(parent, std::move(name), is_inline))
+            {
+            }
+
+            /// \effects Adds an entity.
+            void add_child(std::unique_ptr<cpp_entity> child) noexcept
+            {
+                namespace_->add_child(std::move(child));
+            }
+
+            /// \returns The finished namespace.
+            std::unique_ptr<cpp_namespace> finish() noexcept
+            {
+                return std::move(namespace_);
+            }
+
+            /// \returns A reference to (not yet finished) namespace.
+            const cpp_namespace& get() const noexcept
+            {
+                return *namespace_;
+            }
+
+        private:
+            std::unique_ptr<cpp_namespace> namespace_;
+        };
+
+        /// \returns Whether or not the namespace is an `inline namespace`.
+        bool is_inline() const noexcept
+        {
+            return inline_;
+        }
+
+    private:
+        cpp_namespace(const cpp_entity& parent, std::string name, bool is_inline)
+        : cpp_scope(parent, std::move(name)), inline_(is_inline)
+        {
+        }
+
+        cpp_entity_type do_get_entity_type() const noexcept override;
+
+        bool inline_;
+    };
+} // namespace cppast
+
+#endif // CPPAST_CPP_NAMESPACE_HPP_INCLUDED
diff --git a/include/cppast/cpp_scope.hpp b/include/cppast/cpp_scope.hpp
index da3593a..cae376a 100644
--- a/include/cppast/cpp_scope.hpp
+++ b/include/cppast/cpp_scope.hpp
@@ -44,6 +44,8 @@ namespace cppast
         /// \effects Adds a new child to the scope.
         void add_child(std::unique_ptr<cpp_entity> ptr) noexcept
         {
+            DEBUG_ASSERT(ptr->parent() == *this, detail::precondition_error_handler{},
+                         "parent not set properly");
             children_.push_back(std::move(ptr));
         }
 
diff --git a/include/cppast/detail/assert.hpp b/include/cppast/detail/assert.hpp
index e855936..1093b6e 100644
--- a/include/cppast/detail/assert.hpp
+++ b/include/cppast/detail/assert.hpp
@@ -14,6 +14,11 @@ namespace cppast
         struct assert_handler : debug_assert::set_level<1>, debug_assert::default_handler
         {
         };
+
+        struct precondition_error_handler : debug_assert::set_level<1>,
+                                            debug_assert::default_handler
+        {
+        };
     }
 } // namespace cppast::detail
 
diff --git a/include/cppast/detail/intrusive_list.hpp b/include/cppast/detail/intrusive_list.hpp
index cb5cb9d..94bd3ec 100644
--- a/include/cppast/detail/intrusive_list.hpp
+++ b/include/cppast/detail/intrusive_list.hpp
@@ -29,14 +29,14 @@ namespace cppast
         struct intrusive_list_access
         {
             template <typename U>
-            static T* get_next(const intrusive_list_node<U>& obj)
+            static T* get_next(const U& obj)
             {
                 static_assert(std::is_base_of<U, T>::value, "must be a base");
                 return static_cast<T*>(obj.next_.get());
             }
 
             template <typename U>
-            static T* set_next(intrusive_list_node<U>& obj, std::unique_ptr<T> node)
+            static T* set_next(U& obj, std::unique_ptr<T> node)
             {
                 static_assert(std::is_base_of<U, T>::value, "must be a base");
                 obj.next_ = std::move(node);
diff --git a/src/cpp_entity_type.cpp b/src/cpp_entity_type.cpp
index 4f5525f..b602ad3 100644
--- a/src/cpp_entity_type.cpp
+++ b/src/cpp_entity_type.cpp
@@ -10,6 +10,9 @@ bool cppast::is_scope(cpp_entity_type type) noexcept
 {
     switch (type)
     {
+    case cpp_entity_type::namespace_t:
+        return true;
+
     case cpp_entity_type::file_t:
         break;
     }
diff --git a/src/cpp_namespace.cpp b/src/cpp_namespace.cpp
new file mode 100644
index 0000000..bb8e706
--- /dev/null
+++ b/src/cpp_namespace.cpp
@@ -0,0 +1,14 @@
+// Copyright (C) 2017 Jonathan Müller <jonathanmueller.dev@gmail.com>
+// This file is subject to the license terms in the LICENSE file
+// found in the top-level directory of this distribution.
+
+#include <cppast/cpp_namespace.hpp>
+
+#include <cppast/cpp_entity_type.hpp>
+
+using namespace cppast;
+
+cpp_entity_type cpp_namespace::do_get_entity_type() const noexcept
+{
+    return cpp_entity_type::namespace_t;
+}