diff --git a/libs/cg/include/psemek/cg/dcel.hpp b/libs/cg/include/psemek/cg/dcel.hpp
index 825ac312..d987a78d 100644
--- a/libs/cg/include/psemek/cg/dcel.hpp
+++ b/libs/cg/include/psemek/cg/dcel.hpp
@@ -107,13 +107,14 @@ namespace psemek::cg
 		std::vector<edge_rec> edges;
 		std::vector<face_rec> faces;
 
-		// TODO: const handles
-
 		// TODO: iteration over handles
 
 		struct point_handle;
+		struct point_handle_const;
 		struct edge_handle;
+		struct edge_handle_const;
 		struct face_handle;
+		struct face_handle_const;
 
 		struct point_handle : detail::handle_base<dcel, Index, detail::point_tag>
 		{
@@ -123,7 +124,7 @@ namespace psemek::cg
 
 			edge_handle edge() const;
 
-			void edge(edge_handle h);
+			void edge(edge_handle h) const;
 
 		protected:
 			point_rec & get() const
@@ -134,6 +135,23 @@ namespace psemek::cg
 			}
 		};
 
+		struct point_handle_const : detail::handle_base<dcel const, Index, detail::point_tag>
+		{
+			using detail::handle_base<dcel const, Index, detail::point_tag>::handle_base;
+
+			Point const & data() const;
+
+			edge_handle_const edge() const;
+
+		protected:
+			point_rec const & get() const
+			{
+				assert(this->owner_ != nullptr);
+				assert(this->i_ < this->owner_->points.size());
+				return this->owner_->points[this->i_];
+			}
+		};
+
 		struct edge_handle : detail::handle_base<dcel, Index, detail::edge_tag>
 		{
 			using detail::handle_base<dcel, Index, detail::edge_tag>::handle_base;
@@ -145,10 +163,10 @@ namespace psemek::cg
 			edge_handle twin() const;
 			face_handle face() const;
 
-			void origin(point_handle h);
-			void next(edge_handle h);
-			void twin(edge_handle h);
-			void face(face_handle h);
+			void origin(point_handle h) const;
+			void next(edge_handle h) const;
+			void twin(edge_handle h) const;
+			void face(face_handle h) const;
 
 		protected:
 			edge_rec & get() const
@@ -159,6 +177,26 @@ namespace psemek::cg
 			}
 		};
 
+		struct edge_handle_const : detail::handle_base<dcel const, Index, detail::edge_tag>
+		{
+			using detail::handle_base<dcel const, Index, detail::edge_tag>::handle_base;
+
+			Edge const & data() const;
+
+			point_handle_const origin() const;
+			edge_handle_const next() const;
+			edge_handle_const twin() const;
+			face_handle_const face() const;
+
+		protected:
+			edge_rec const & get() const
+			{
+				assert(this->owner_ != nullptr);
+				assert(this->i_ < this->owner_->edges.size());
+				return this->owner_->edges[this->i_];
+			}
+		};
+
 		struct face_handle : detail::handle_base<dcel, Index, detail::face_tag>
 		{
 			using detail::handle_base<dcel, Index, detail::face_tag>::handle_base;
@@ -167,7 +205,7 @@ namespace psemek::cg
 
 			edge_handle edge() const;
 
-			void edge(edge_handle h);
+			void edge(edge_handle h) const;
 
 		protected:
 			face_rec & get() const
@@ -178,6 +216,23 @@ namespace psemek::cg
 			}
 		};
 
+		struct face_handle_const : detail::handle_base<dcel const, Index, detail::face_tag>
+		{
+			using detail::handle_base<dcel const, Index, detail::face_tag>::handle_base;
+
+			Face const & data() const;
+
+			edge_handle_const edge() const;
+
+		protected:
+			face_rec const & get() const
+			{
+				assert(this->owner_ != nullptr);
+				assert(this->i_ < this->owner_->faces.size());
+				return this->owner_->faces[this->i_];
+			}
+		};
+
 		point_handle point(Index i)
 		{
 			return {this, i};
@@ -193,6 +248,21 @@ namespace psemek::cg
 			return {this, i};
 		}
 
+		point_handle_const point(Index i) const
+		{
+			return {this, i};
+		}
+
+		edge_handle_const edge(Index i) const
+		{
+			return {this, i};
+		}
+
+		face_handle_const face(Index i) const
+		{
+			return {this, i};
+		}
+
 		point_handle push_point(Point data = {})
 		{
 			auto i = static_cast<Index>(points.size());
@@ -315,11 +385,23 @@ namespace psemek::cg
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::point_handle::edge(edge_handle h)
+	void dcel<Point, Edge, Face, Index>::point_handle::edge(edge_handle h) const
 	{
 		get().edge = h.index();
 	}
 
+	template <typename Point, typename Edge, typename Face, typename Index>
+	Point const & dcel<Point, Edge, Face, Index>::point_handle_const::data() const
+	{
+		return get().data();
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::edge_handle_const dcel<Point, Edge, Face, Index>::point_handle_const::edge() const
+	{
+		return edge_handle_const{this->owner_, get().edge};
+	}
+
 	template <typename Point, typename Edge, typename Face, typename Index>
 	Edge & dcel<Point, Edge, Face, Index>::edge_handle::data() const
 	{
@@ -351,29 +433,59 @@ namespace psemek::cg
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::edge_handle::origin(point_handle h)
+	void dcel<Point, Edge, Face, Index>::edge_handle::origin(point_handle h) const
 	{
 		get().origin = h.index();
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::edge_handle::next(edge_handle h)
+	void dcel<Point, Edge, Face, Index>::edge_handle::next(edge_handle h) const
 	{
 		get().next = h.index();
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::edge_handle::twin(edge_handle h)
+	void dcel<Point, Edge, Face, Index>::edge_handle::twin(edge_handle h) const
 	{
 		get().twin = h.index();
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::edge_handle::face(face_handle h)
+	void dcel<Point, Edge, Face, Index>::edge_handle::face(face_handle h) const
 	{
 		get().face = h.index();
 	}
 
+	template <typename Point, typename Edge, typename Face, typename Index>
+	Edge const & dcel<Point, Edge, Face, Index>::edge_handle_const::data() const
+	{
+		return get().data();
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::point_handle_const dcel<Point, Edge, Face, Index>::edge_handle_const::origin() const
+	{
+		return point_handle_const{this->owner_, get().origin};
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::edge_handle_const dcel<Point, Edge, Face, Index>::edge_handle_const::next() const
+	{
+		return edge_handle_const{this->owner_, get().next};
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::edge_handle_const dcel<Point, Edge, Face, Index>::edge_handle_const::twin() const
+	{
+		return edge_handle_const{this->owner_, get().twin};
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::face_handle_const dcel<Point, Edge, Face, Index>::edge_handle_const::face() const
+	{
+		return face_handle_const{this->owner_, get().face};
+	}
+
 	template <typename Point, typename Edge, typename Face, typename Index>
 	Face & dcel<Point, Edge, Face, Index>::face_handle::data() const
 	{
@@ -387,11 +499,23 @@ namespace psemek::cg
 	}
 
 	template <typename Point, typename Edge, typename Face, typename Index>
-	void dcel<Point, Edge, Face, Index>::face_handle::edge(edge_handle h)
+	void dcel<Point, Edge, Face, Index>::face_handle::edge(edge_handle h) const
 	{
 		get().edge = h.index();
 	}
 
+	template <typename Point, typename Edge, typename Face, typename Index>
+	Face const & dcel<Point, Edge, Face, Index>::face_handle_const::data() const
+	{
+		return get().data();
+	}
+
+	template <typename Point, typename Edge, typename Face, typename Index>
+	typename dcel<Point, Edge, Face, Index>::edge_handle_const dcel<Point, Edge, Face, Index>::face_handle_const::edge() const
+	{
+		return edge_handle_const{this->owner_, get().edge};
+	}
+
 	template <
 		typename Point2, typename Edge2 = util::empty, typename Face2 = util::empty, typename Index2 = std::size_t,
 		typename Point, typename Edge, typename Face, typename Index,