taru-adjective, adverb taking the 'to' particle
quiet and secluded; tranquil and remote
A literary, somewhat archaic word describing a deeply quiet, isolated, and serene atmosphere, often of a place in nature. Used as a たる adjective or with と adverbially.
山奥の寺は幽然とした静けさに包まれていた。
The temple deep in the mountains was wrapped in a quiet and secluded stillness.
谷底には幽然と霧が立ちこめていた。
Mist hung quietly and remotely in the valley bottom.