General:
* Tranquil
* Peaceful
* Serene
* Still
* Silent
* Calm
* Soothing
* Unhurried
* Undisturbed
* Reposeful
* Solitary
Descriptive:
* Hush-hush
* Muted
* Soundless
* Noiseless
* Ethereal
* Dreamy
* Contemplative
* Secluded
* Remote
* Isolated
Figurative:
* As quiet as a mouse
* As silent as the grave
* A sanctuary of peace
* A haven of tranquility
Words related to specific senses:
* Visual: Peaceful, serene, restful, uncluttered, calming, soft-lit, muted, ethereal, dreamy
* Auditory: Quiet, silent, hushed, soundless, noiseless, whisper-quiet,
* Tactile: Smooth, soft, velvety, cool, comfortable, cozy, comforting
* Olfactory: Fragrant, aromatic, sweet-smelling, fresh, earthy, clean
The best word to use depends on the specific feeling you want to evoke.