The phrase "undiscovered land" refers to a place or area that hasn't been explored or found by people before. It usually implies a sense of adventure and the potential for new discoveries. Full definition
In this first of five books now available in English, he makes the audacious claim to have explored undiscovered land in an unknown world. (faith.org.uk)
I feel an irresistible tug towards undiscovered lands. (nakedpastor.com)
Navigators were dispatched in search of undiscovered lands whenever an island started to become overpopulated. (keliiskayak.com)