Land of the Lost - 2x04 - One of our Pylons is Missing

Cha-Ka and the Marshalls discover a huge power source beneath the Land of the Lost.
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The Marshalls (along with Cha-Ka) decide to follow the pylons, which are each located a quarter mile apart, to see if the pattern holds true. Cha-Ka, who is carrying a lunch basket, is scared off by Spot. A hole mysteriously appears in the ground and swallows Spot up before disappearing, to Cha-Ka's relief and surprise. Unbeknownst to him, the hole reappears and swallows up the lunch basket.

The Marshalls find Cha-Ka, who explains that the ground swallowed the coelophysis and the lunch basket up. At first the Marshalls are doubtful, but the hole reappears and swallows Cha-Ka. Will and Rick, who recognize that this is where the next pylon should be located, head for the last pylon while Holly keeps watch.

Holly ties a vine around her waist and begins digging in the dirt. She discovers a large metal circle. Meanwhile, Will and Rick enter the pylon and are given a vision of Holly as she too falls through the hole. They rush back and Rick secures himself with a vine to rescue Holly.

The vine suspending Holly in the hole breaks and she falls. Finally she slows down and begins to orbit a red, pulsating, irregularly shaped object, around which circle Cha-Ka, the lunch basket, and Spot as well. Rick falls in moments later and begins to orbit the object(which he likens to "a generator or a giant heart"). The Generator shoots out a beam of light which causes Spot to be absorbed. Rick takes out his code mirror and bounces a beam back into the Generator, which ultimately causes the orbiting people to be propelled back up through the hole to Will, followed shortly thereafter by the lunch basket.

https://en.wikipedia.org/wiki/One_of_Our_Pylons_Is_Missing