diff --git a/btree.h b/btree.h
index f7e26b3..aae571c 100644
--- a/btree.h
+++ b/btree.h
@@ -299,6 +299,22 @@ namespace persistent_data {
 		// free the on disk btree when the destructor is called
 		void destroy();
 
+
+		// Derive a class from this base class if you need to
+		// inspect the individual nodes that make up a btree.
+		class visitor {
+		public:
+			virtual ~visitor() {}
+			typedef boost::shared_ptr<visitor> ptr;
+
+			virtual void visit_internal(unsigned level, btree_detail::node_ref<uint64_traits, BlockSize> const &n) = 0;
+			virtual void visit_internal_leaf(unsigned level, btree_detail::node_ref<uint64_traits, BlockSize> const &n) = 0;
+			virtual void visit_leaf(unsigned level, btree_detail::node_ref<ValueTraits, BlockSize> const &n) = 0;
+		};
+
+		// Walks the tree in depth first order
+		void visit(typename visitor::ptr visitor);
+
 	private:
 		template <typename ValueTraits2>
 		void split_node(btree_detail::shadow_spine<BlockSize> &spine,
@@ -321,6 +337,9 @@ namespace persistent_data {
 				uint64_t key,
 				int *index);
 
+		void walk_tree(typename visitor::ptr visitor,
+			       unsigned level, block_address b);
+
 		typename persistent_data::transaction_manager<BlockSize>::ptr tm_;
 		bool destroy_;
 		block_address root_;
diff --git a/btree.tcc b/btree.tcc
index 7b84efe..3b51eab 100644
--- a/btree.tcc
+++ b/btree.tcc
@@ -590,5 +590,36 @@ insert_location(btree_detail::shadow_spine<BlockSize> &spine,
 		(leaf.key_at(i) != key));
 }
 
+template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
+void
+btree<Levels, ValueTraits, BlockSize>::visit(typename visitor::ptr visitor)
+{
+	walk_tree(visitor, 0, root_);
+}
+
+template <unsigned Levels, typename ValueTraits, uint32_t BlockSize>
+void
+btree<Levels, ValueTraits, BlockSize>::
+walk_tree(typename visitor::ptr visitor,
+	  unsigned level, block_address b)
+{
+	using namespace btree_detail;
+	auto blk = tm_->read_lock(b);
+	auto o = to_node<uint64_traits, BlockSize>(blk);
+	if (o.get_type() == INTERNAL) {
+		visitor->visit_internal(level, o);
+		for (unsigned i = 0; i < o.get_nr_entries(); i++)
+			walk_tree(visitor, level, o.value_at(i));
+
+	} else if (level < Levels - 1) {
+		visitor->visit_internal_leaf(level, o);
+		for (unsigned i = 0; i < o.get_nr_entries(); i++)
+			walk_tree(visitor, level + 1, o.value_at(i));
+
+	} else {
+		auto ov = to_node<ValueTraits, BlockSize>(blk);
+		visitor->visit_leaf(level, ov);
+	}
+}
 
 //----------------------------------------------------------------
diff --git a/unit-tests/btree_t.cc b/unit-tests/btree_t.cc
index 87f30da..fa40eb0 100644
--- a/unit-tests/btree_t.cc
+++ b/unit-tests/btree_t.cc
@@ -30,6 +30,28 @@ namespace {
 			new btree<1, uint64_traits, 4096>(
 				create_tm(), rc));
 	}
+
+	class constraint_visitor : public btree<1, uint64_traits, 4096>::visitor {
+	private:
+		void visit_internal(unsigned level, btree_detail::node_ref<uint64_traits, 4096> const &n) {
+			// cout << "internal: level = " << level << ", nr_entries = " << n.get_nr_entries() << endl;
+		}
+
+		void visit_internal_leaf(unsigned level, btree_detail::node_ref<uint64_traits, 4096> const &n) {
+			// cout << "internal_leaf !" << endl;
+		}
+
+		void visit_leaf(unsigned level, btree_detail::node_ref<uint64_traits, 4096> const &n) {
+			// cout << "leaf: level = " << level << ", nr_entries = " << n.get_nr_entries() << endl;
+		}
+	};
+
+	void check_constraints(btree<1, uint64_traits, 4096>::ptr tree) {
+		typedef btree<1, uint64_traits, 4096> tree_type;
+
+		typename tree_type::visitor::ptr v(new constraint_visitor);
+		tree->visit(v);
+	}
 }
 
 //----------------------------------------------------------------