Shimizu, besides other changes, designed the main stone bridge of the garden, known as Koko-kyo, the "straddling rainbow bridge". He was inspired by an older type of "moon bridge", which is named like this because together with the reflection on water it creates a perfect circle. The Koko-kyo has a similar but different shape, suggesting a rainbow, hence its name...
EXIF info:
Nikon D90
Lens: 8-16mm F/4.5-5.6G
Focal Length: 16mm
Aperture: F/7.1
Shutter Speed: 1/640s
ISO Sensitivity: ISO 200