diff --git a/cartographer/mapping_2d/local_trajectory_builder.cc b/cartographer/internal/mapping_2d/local_trajectory_builder.cc
similarity index 99%
rename from cartographer/mapping_2d/local_trajectory_builder.cc
rename to cartographer/internal/mapping_2d/local_trajectory_builder.cc
index 6ca7d67..03b43ad 100644
--- a/cartographer/mapping_2d/local_trajectory_builder.cc
+++ b/cartographer/internal/mapping_2d/local_trajectory_builder.cc
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "cartographer/mapping_2d/local_trajectory_builder.h"
+#include "cartographer/internal/mapping_2d/local_trajectory_builder.h"
 
 #include <limits>
 #include <memory>
diff --git a/cartographer/mapping_2d/local_trajectory_builder.h b/cartographer/internal/mapping_2d/local_trajectory_builder.h
similarity index 95%
rename from cartographer/mapping_2d/local_trajectory_builder.h
rename to cartographer/internal/mapping_2d/local_trajectory_builder.h
index 66cdfab..ac8f483 100644
--- a/cartographer/mapping_2d/local_trajectory_builder.h
+++ b/cartographer/internal/mapping_2d/local_trajectory_builder.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef CARTOGRAPHER_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
-#define CARTOGRAPHER_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
+#ifndef CARTOGRAPHER_INTERNAL_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
+#define CARTOGRAPHER_INTERNAL_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
 
 #include <memory>
 
@@ -109,4 +109,4 @@ class LocalTrajectoryBuilder {
 }  // namespace mapping_2d
 }  // namespace cartographer
 
-#endif  // CARTOGRAPHER_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
+#endif  // CARTOGRAPHER_INTERNAL_MAPPING_2D_LOCAL_TRAJECTORY_BUILDER_H_
diff --git a/cartographer/mapping_3d/local_trajectory_builder.cc b/cartographer/internal/mapping_3d/local_trajectory_builder.cc
similarity index 99%
rename from cartographer/mapping_3d/local_trajectory_builder.cc
rename to cartographer/internal/mapping_3d/local_trajectory_builder.cc
index 984ac04..897ff7f 100644
--- a/cartographer/mapping_3d/local_trajectory_builder.cc
+++ b/cartographer/internal/mapping_3d/local_trajectory_builder.cc
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "cartographer/mapping_3d/local_trajectory_builder.h"
+#include "cartographer/internal/mapping_3d/local_trajectory_builder.h"
 
 #include <memory>
 
diff --git a/cartographer/mapping_3d/local_trajectory_builder.h b/cartographer/internal/mapping_3d/local_trajectory_builder.h
similarity index 94%
rename from cartographer/mapping_3d/local_trajectory_builder.h
rename to cartographer/internal/mapping_3d/local_trajectory_builder.h
index 2a7b446..4e3298a 100644
--- a/cartographer/mapping_3d/local_trajectory_builder.h
+++ b/cartographer/internal/mapping_3d/local_trajectory_builder.h
@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 
-#ifndef CARTOGRAPHER_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
-#define CARTOGRAPHER_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
+#ifndef CARTOGRAPHER_INTERNAL_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
+#define CARTOGRAPHER_INTERNAL_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
 
 #include <memory>
 
@@ -97,4 +97,4 @@ class LocalTrajectoryBuilder {
 }  // namespace mapping_3d
 }  // namespace cartographer
 
-#endif  // CARTOGRAPHER_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
+#endif  // CARTOGRAPHER_INTERNAL_MAPPING_3D_LOCAL_TRAJECTORY_BUILDER_H_
diff --git a/cartographer/mapping_3d/local_trajectory_builder_test.cc b/cartographer/internal/mapping_3d/local_trajectory_builder_test.cc
similarity index 99%
rename from cartographer/mapping_3d/local_trajectory_builder_test.cc
rename to cartographer/internal/mapping_3d/local_trajectory_builder_test.cc
index ee2c81a..b45a7eb 100644
--- a/cartographer/mapping_3d/local_trajectory_builder_test.cc
+++ b/cartographer/internal/mapping_3d/local_trajectory_builder_test.cc
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-#include "cartographer/mapping_3d/local_trajectory_builder.h"
+#include "cartographer/internal/mapping_3d/local_trajectory_builder.h"
 
 #include <memory>
 #include <random>
diff --git a/cartographer/mapping/map_builder.cc b/cartographer/mapping/map_builder.cc
index f9a8d78..e5ab746 100644
--- a/cartographer/mapping/map_builder.cc
+++ b/cartographer/mapping/map_builder.cc
@@ -25,9 +25,9 @@
 #include "cartographer/common/make_unique.h"
 #include "cartographer/common/time.h"
 #include "cartographer/internal/mapping/global_trajectory_builder.h"
+#include "cartographer/internal/mapping_2d/local_trajectory_builder.h"
+#include "cartographer/internal/mapping_3d/local_trajectory_builder.h"
 #include "cartographer/mapping/collated_trajectory_builder.h"
-#include "cartographer/mapping_2d/local_trajectory_builder.h"
-#include "cartographer/mapping_3d/local_trajectory_builder.h"
 #include "cartographer/sensor/range_data.h"
 #include "cartographer/sensor/voxel_filter.h"
 #include "cartographer/transform/rigid_transform.h"