Fortunately, the gate also survived to the recent devastating earthquake - I was able to confirm that via the high resolution imagery of Tokyo after earthquake, provided by Google.
The mausoleum was built in 1632 by Tokugawa Iemitsu, the third shogun of the Tokugawa dynasty, dedicated to his father, Tokugawa Hidetada (also known as Daitoku-in, hence the name of the mausoleum).
By night, the gate was spectacularly illuminated... but because of the recent, sad events, it is probably dark now...
EXIF info:
Nikon D90
Lens: VR 18-55mm F/3.5-5.6G
Focal Length: 25mm
Aperture: F/7.1
Shutter Speed: 2.5s
ISO Sensitivity: ISO 200