heyday, peak
当時、芸術は全盛でした。
At that time, the arts were flourishing.
当時その宗教は全盛だった。
That religion was at its height at the time.
彼女にも全盛時代があった。
She had her heyday, too.
その歌手はその歌のときが全盛でした。
The singer was at the peak of their career when they recorded that song.