In Westworld Season 3 Episode 7, Dolores brought Caleb to a place important to him, and Bernard and Stubbs investigated the facility where they found William.
In the previous episode of HBO’s Westworld, Serac revealed that Charlotte Hale was a Dolores host, and Bernard and Stubbs found William at the psychiatric facility.
Bernard and Stubbs revealed to William that he is a host and that Serac had successfully stolen Delos.
It reminded Dolores of where she was from, but she was also taking Caleb somewhere important to his past.