Eternity
Perpetuity, Permanence
noun, な adjective, の adjective
Leisure that last for a long time ends up going on for all eternity. It never ends, and why should it? You're soooo relaaaaaxed, you can't possibly ever stop.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
悠久な大自然で、人生について色々なことを考えてみました。
I thought about various things about human life within the eternity of mother nature.