Gu Byauk Gyi is one of the Bagan temples where the interior matters as much as the silhouette. From outside it reads as another brick shrine in a plain full of them; inside, the walls preserve delicate painted scenes from the Jataka stories, best appreciated slowly as your eyes adjust to the low light.
It is a strong stop near Myinkaba, especially if you want Bagan to be more than sunrise viewpoints and temple-counting. Bring a small torch if permitted, move gently, and remember that the best details here are fragile rather than grand.