Kingdom Of Heaven, Heaven, Paradise
noun, の adjective
This is heaven country. Where is that? Probably just in heaven (or if you want to be fancy, the kingdom of heaven).
てんごく
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. The 国 is changed to the reading ごく though because of rendaku. Even heaven changes a little bit.
これは、天国にいる母へのメッセージです。
This is a message to my mother in heaven.
ここは、まるでコスプレイヤーの天国だ。
This is like a paradise for cosplayers.
天国がこんなとこだったなんて、がっかりです。
I'm disappointed that heaven was like this.