The also needed to be train tunnels through the mountain. The main one was a long tunnel for the complete circular track. At the bottom there needed to be a second tunnel for the slate carrying train to disappear to unload the slates, and at the top there needed to be a tunnel into for the OO train to appear to leave.

The tunnels running through the mountain were framed in wood to protect them from the mountain above, and the two main tunnels had wooden frames in the backs to allow access to the track from outside. The third tunnel by the short stretch of 00 track was simply for scenic effect.