I think he was referring to the Replicator tool . You can replicate the terrain using the seamless function. Try the following: 1.add a terrain object. 2.drag the replicator icon to the scene. 3.In the sequencer drag the terrain object onto the replicator item to create a parent child relationship 4.double click the replicator item in the sequencer to go to the replicator editor. 5.For the Replication method use Autogrid. 6.Choose an appropriate number of objects. 7 Then choose Seamless at the bottom of the editor window. You should have tiling terrains now, the terrain object can be a Surface replicating group too ,I find the replicating tools to be very flexible. Hope this helps.