Formal:
* Labyrinth: A complex network of winding passages, often with a single entrance and exit.
* Maze: Similar to a labyrinth, but usually more intricate and with multiple paths.
* Intricate network: Emphasizes the complexity and interconnectedness of the passages.
* Interlacing corridors: Focuses on the overlapping and intersecting nature of the passages.
* Tangled web: Implies a chaotic and confusing arrangement of passages.
Informal:
* Twisting tunnels: Suggests a sense of adventure and exploration.
* Winding paths: A more general term for a network of paths that turn and twist.
* Snaking passages: Creates a visual image of the passages winding and turning like a snake.
* Crazy corridors: A more whimsical and playful term for a confusing network of passages.
Literary:
* A web of passageways: A poetic and evocative way to describe the network of passages.
* A labyrinthine network: Emphasizes the complexity and difficulty of navigating the passages.
* A subterranean maze: Focuses on the underground nature of the passages.
The best word to use will depend on the specific context of your writing. Consider the tone, the setting, and the overall meaning you want to convey.