The fine visible grid is from a net they have stretched across the space. The architecture is a famous example of the work of Kingo Tatsuno. The eight relief carvings you see at the corners of the octagonal ceiling are of eagles (often mistaken for hawks or other birds). These are part of a larger zodiac theme throughout the dome; while eight of the zodiac animals are represented in these corners, the remaining four (the rat, horse, rabbit, and rooster) are famously located in a different city (Takeo Onsen) as part of a historical architectural puzzle/adventure.
by photobombolo