A natural area of tilted sandstone in California where Raffi Musiker lived in seclusion in 2399, and in reality a filming location used by Star Trek since the 1960s.
Vasquez Rocks is a park of jagged sandstone outcrops north of Los Angeles. Within the fiction it is where Raffi Musiker has withdrawn to a small cabin after losing her Starfleet career. Picard seeks her out there at the end of Maps and Legends and in The End Is the Beginning, asking for help in finding a ship and a pilot.
The choice of setting is a nod to production history. The rocks stood in for alien worlds in several original series episodes, most famously as the place where Kirk fights the Gorn captain in Arena, and they were used again in later series and films, including as the surface of Vulcan.
Picard shows the place as itself, with an on-screen caption giving its real name.