Senjokaku can be translated as the "hall of one thousand tatami mats", a figurative name to refer to a very large building - the largest structure on Miyajima Island. But the fact is that, traditionally, the size of the rooms is measured in Japan in tatami mats. For example, the traditional tea rooms have a surface of 4½ mats and the shops have about 5½ mats. Of course, there are also differences from zone to zone, because the standard tatami size varies a little: from 0.88 x 1.76 meters in Tokyo, to 0.955 x 1.91 meters in Kyoto...
EXIF info:
Nikon D300
Lens: 8-16mm F/4.5-5.6G
Focal Length: 16mm
Aperture: F/7.1
Shutter Speed: 1/250s
ISO Sensitivity: ISO 250