In times long past, this planet was the home of a mighty and noble race of beings which called themselves the Krell.
11 seconds sound clip from the Forbidden Planet (1956) movie soundboard.
You can hear this line at 00:49:58 in the Blu-ray version of the movie.
Quote context
[...]
- You'll find the household silver in the dining room and my daughter's jewelry on her dressing table.
- Last night our klystron monitor was sabotaged.
- Then the time has come for clarification. Sit down.
- Ethically, as well as technologically, they were a million years ahead of humankind...
- For in unlocking the mysteries of nature, they had conquered even their baser selves.
- I see, that explains the tiger and the deer.
[...]