Sanxianshan Scenic Area is a large themed park in Penglai built around the Taoist myth of the three immortal mountains. It is modern and staged, but that fits Penglai's long association with sea legends, immortals, and mirage-like islands.
Expect pavilions, lakes, bridges, and carefully composed views rather than an ancient ruin. It is most useful if you want another mythic-Penglai stop after Penglai Pavilion and the seafront.