The Morlock Tunnels were a series of underground tunnels and passages that existed in the future world of Mor. They were connected to the surface by a series of wells, which each had a ladder leading up the long shaft. The tunnels also connected to a number of other structures left behind by Humanity, such as the Palace of Green Porcelain, whose hallways gradually lead deeper below the Earth. The Morlock Sphinxes also contained entrances to their caverns. The caverns are generally too dark for Humans to see, which is comfortable for the nocturnal Morlocks. ("The Time Machine")
The various sections of the tunnels are connected by The Hub, a central point which has dozens of tunnels leading off in different directions. Some of which are large enough for the Giant Mantises to go back and forth in, doing tasks for the Morlocks. Some of the tunnels also lead to advanced science labs. New tunnels can be quickly formed as needed using nanotechnology. ("The Wee Time Traveler")
The Morlock tunnels also lead into the underground city of Foss, where the Morloi people lived for many years. ("Beyond the Time Machine")