Untroubled (adjective)

1. Not disturbed or upset.
2. Free from worries or problems.
3. Calm and peaceful.

Origin:

Middle english, from un- + troubled.

Examples:

1. The untroubled sleep was refreshing for the exhausted traveler.
2. The untroubled surface of the lake was disturbed by the jumping fish.
3. The untroubled mind of the yogi was achieved through meditation.
4. The untroubled sky was a perfect backdrop for the fireworks display.
5. The untroubled expression on her face showed she was content.