Glossary of Images and Related Explanations in the Revelation:

The One Sitting on the Throne"

...and behold, a throne was standing in heaven, and One sitting on the throne. 3 And He who was sitting was like a jasper stone and a sardius in appearance....5 And from the throne proceed flashes of lightning and sounds and peals of thunder..."
Revelation 4:2-5 (NAS)