diff --git a/src/main/java/com/sk89q/worldedit/operation/BreadthFirstSearch.java b/src/main/java/com/sk89q/worldedit/operation/BreadthFirstSearch.java
new file mode 100644
index 000000000..47d9feaa5
--- /dev/null
+++ b/src/main/java/com/sk89q/worldedit/operation/BreadthFirstSearch.java
@@ -0,0 +1,172 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.BlockVector;
+import com.sk89q.worldedit.Vector;
+import com.sk89q.worldedit.WorldEditException;
+
+import java.util.*;
+
+/**
+ * Performs a breadth-first search starting from points added with
+ * {@link #visit(com.sk89q.worldedit.Vector)}. The search continues
+ * to a certain adjacent point provided that the method
+ * {@link #isVisitable(com.sk89q.worldedit.Vector, com.sk89q.worldedit.Vector)}
+ * returns true for that point.
+ * </p>
+ * As an abstract implementation, this class can be used to implement
+ * functionality that starts at certain points and extends outward from
+ * those points.
+ */
+public abstract class BreadthFirstSearch implements Operation {
+
+    private final RegionFunction function;
+    private final Queue<BlockVector> queue = new ArrayDeque<BlockVector>();
+    private final Set<BlockVector> visited = new HashSet<BlockVector>();
+    private final List<Vector> directions = new ArrayList<Vector>();
+    private int affected = 0;
+
+    /**
+     * Create a new instance.
+     *
+     * @param function the function to apply to visited blocks
+     */
+    public BreadthFirstSearch(RegionFunction function) {
+        this.function = function;
+        addAxes();
+    }
+
+    /**
+     * Get the list of directions will be visited.
+     * </p>
+     * Directions are {@link com.sk89q.worldedit.Vector}s that determine
+     * what adjacent points area available. Vectors should not be
+     * unit vectors. An example of a valid direction is {@code new Vector(1, 0, 1)}.
+     * </p>
+     * The list of directions can be cleared.
+     *
+     * @return the list of directions
+     */
+    protected List<Vector> getDirections() {
+        return directions;
+    }
+
+    /**
+     * Add the directions along the axes as directions to visit.
+     */
+    protected void addAxes() {
+        directions.add(new Vector(0, -1, 0));
+        directions.add(new Vector(0, 1, 0));
+        directions.add(new Vector(-1, 0, 0));
+        directions.add(new Vector(1, 0, 0));
+        directions.add(new Vector(0, 0, -1));
+        directions.add(new Vector(0, 0, 1));
+    }
+
+    /**
+     * Add the diagonal directions as directions to visit.
+     */
+    protected void addDiagonal() {
+        directions.add(new Vector(1, 0, 1));
+        directions.add(new Vector(-1, 0, -1));
+        directions.add(new Vector(1, 0, -1));
+        directions.add(new Vector(-1, 0, 1));
+    }
+
+    /**
+     * Add the given location to the list of locations to visit, provided
+     * that it has not been visited. The position passed to this method
+     * will still be visited even if it fails
+     * {@link #isVisitable(com.sk89q.worldedit.Vector, com.sk89q.worldedit.Vector)}.
+     * </p>
+     * This method should be used before the search begins, because if
+     * the position <em>does</em> fail the test, and the search has already
+     * visited it (because it is connected to another root point),
+     * the search will mark the position as "visited" and a call to this
+     * method will do nothing.
+     *
+     * @param position the position
+     */
+    public void visit(Vector position) {
+        BlockVector blockVector = position.toBlockVector();
+        if (!visited.contains(blockVector)) {
+            queue.add(blockVector);
+            visited.add(blockVector);
+        }
+    }
+
+    /**
+     * Try to visit the given 'to' location.
+     *
+     * @param from the origin block
+     * @param to the block under question
+     */
+    private void visit(Vector from, Vector to) {
+        BlockVector blockVector = to.toBlockVector();
+        if (!visited.contains(blockVector)) {
+            visited.add(blockVector);
+            if (isVisitable(from, to)) {
+                queue.add(blockVector);
+            }
+        }
+    }
+
+    /**
+     * Return whether the given 'to' block should be visited, starting from the
+     * 'from' block.
+     *
+     * @param from the origin block
+     * @param to the block under question
+     * @return true if the 'to' block should be visited
+     */
+    protected abstract boolean isVisitable(Vector from, Vector to);
+
+    /**
+     * Get the number of affected objects.
+     *
+     * @return the number of affected
+     */
+    public int getAffected() {
+        return affected;
+    }
+
+    @Override
+    public Operation resume() throws WorldEditException {
+        Vector position;
+        
+        while ((position = queue.poll()) != null) {
+            if (function.apply(position)) {
+                affected++;
+            }
+
+            for (Vector dir : directions) {
+                visit(position, position.add(dir));
+            }
+        }
+
+        return null;
+    }
+
+    @Override
+    public void cancel() {
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/com/sk89q/worldedit/operation/DownwardVisitor.java b/src/main/java/com/sk89q/worldedit/operation/DownwardVisitor.java
new file mode 100644
index 000000000..393ca35c7
--- /dev/null
+++ b/src/main/java/com/sk89q/worldedit/operation/DownwardVisitor.java
@@ -0,0 +1,66 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.EditSession;
+import com.sk89q.worldedit.Vector;
+import com.sk89q.worldedit.masks.Mask;
+
+import java.util.List;
+
+/**
+ * Visits adjacent points on the same X-Z plane as long as the points
+ * pass the given mask, and then executes the provided region
+ * function on the entire column.
+ * </p>
+ * This is used by <code>//fill</code>.
+ */
+public class DownwardVisitor extends RecursiveVisitor {
+
+    private int baseY;
+
+    /**
+     * Create a new visitor.
+     *
+     * @param editSession the edit session
+     * @param mask the mask
+     * @param function the function
+     * @param baseY the base Y
+     */
+    public DownwardVisitor(EditSession editSession, Mask mask, RegionFunction function, int baseY) {
+        super(editSession, mask, function);
+
+        this.baseY = baseY;
+
+        List<Vector> directions = getDirections();
+        directions.clear();
+        directions.add(new Vector(1, 0, 0));
+        directions.add(new Vector(-1, 0, 0));
+        directions.add(new Vector(0, 0, 1));
+        directions.add(new Vector(0, 0, -1));
+        directions.add(new Vector(0, -1, 0));
+    }
+
+    @Override
+    protected boolean isVisitable(Vector from, Vector to) {
+        int fromY = from.getBlockY();
+        return (fromY == baseY || to.subtract(from).getBlockY() < 0) && super.isVisitable(from, to);
+    }
+}
diff --git a/src/main/java/com/sk89q/worldedit/operation/RecursiveVisitor.java b/src/main/java/com/sk89q/worldedit/operation/RecursiveVisitor.java
new file mode 100644
index 000000000..7bc6eb82c
--- /dev/null
+++ b/src/main/java/com/sk89q/worldedit/operation/RecursiveVisitor.java
@@ -0,0 +1,49 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.EditSession;
+import com.sk89q.worldedit.Vector;
+import com.sk89q.worldedit.masks.Mask;
+
+/**
+ * An implementation of an {@link BreadthFirstSearch} that uses a mask to
+ * determine where a block should be visited.
+ */
+public class RecursiveVisitor extends BreadthFirstSearch {
+
+    private final EditSession editSession;
+    private final Mask mask;
+
+    public RecursiveVisitor(EditSession editSession, Mask mask, RegionFunction function) {
+        super(function);
+        this.editSession = editSession;
+        this.mask = mask;
+    }
+
+    @Override
+    protected boolean isVisitable(Vector from, Vector to) {
+        int y = to.getBlockY();
+        if (y < 0 || y > editSession.getWorld().getMaxY()) {
+            return false;
+        }
+        return mask.matches(editSession, to);
+    }
+}
diff --git a/src/main/java/com/sk89q/worldedit/operation/RegionVisitor.java b/src/main/java/com/sk89q/worldedit/operation/RegionVisitor.java
new file mode 100644
index 000000000..51772d57b
--- /dev/null
+++ b/src/main/java/com/sk89q/worldedit/operation/RegionVisitor.java
@@ -0,0 +1,65 @@
+/*
+ * WorldEdit, a Minecraft world manipulation toolkit
+ * Copyright (C) sk89q <http://www.sk89q.com>
+ * Copyright (C) WorldEdit team and contributors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.sk89q.worldedit.operation;
+
+import com.sk89q.worldedit.Vector;
+import com.sk89q.worldedit.WorldEditException;
+import com.sk89q.worldedit.regions.Region;
+
+/**
+ * Utility class to apply region functions to {@link com.sk89q.worldedit.regions.Region}.
+ */
+public class RegionVisitor implements Operation {
+
+    private final Region region;
+    private final RegionFunction function;
+    private int affected = 0;
+
+    public RegionVisitor(Region region, RegionFunction function) {
+        this.region = region;
+        this.function = function;
+    }
+
+    /**
+     * Get the number of affected objects.
+     *
+     * @return the number of affected
+     */
+    public int getAffected() {
+        return affected;
+    }
+
+    @Override
+    public Operation resume() throws WorldEditException {
+        for (Vector pt : region) {
+            if (function.apply(pt)) {
+                affected++;
+            }
+        }
+
+        return null;
+    }
+
+    @Override
+    public void cancel() {
+    }
+
+}
+