Ajisai no Miya: Fujinomori jinjya!, a set on Flickr.
Fujinomori Shrine has a long history. It was built before the relocation of the capital to Kyoto in 794. The shrine deifies twelve gods including Susanoono Mikoto, who are venerated as Ubusunagami (tutelary gods of hamlets) of Fukakusa area in the south of Kyoto.
The shrine is known as a place where the festival Shobu no Sakku (Iris Festival) originally started. People believe in the deity of the shrine for horses and winning in competition. There are two reasons for this. One of the reasons is that the Japanese words for ‘Iris’ and ‘battle’ are the same in pronunciation (i.e., both of them are pronounced ‘shobu’). The other reasons is that the Fujinomori Festival, which is held on May 5 every year, includes a thrilling religious event called Kakeuma Shinji, when horseback riders thrill spectators with spectacular stunts. The enshrined gods include Prince Toneri, the first scholar of Japan and the editor of the Nihonshoki (chronicles of Japan). Therefore, people believe in the deity of the shrine for learning as well.
It is said that the main hall was granted in 1712 by Emperor Nakamikado and that it had been used as the office in the Imperial Court, known as the Naisho-dokoro (Kashikodokoro). The Hachimangu inner sanctuary located in the East behind the main hall and the Taishogun inner sanctuary located int he west are designated as important cultural properties. 
Moreover, there is a noted spring named Fujinomizu, which means water never found in other places, in the east of the main hall.
The shrine hydrangeas that blossom out in June are famous, and that is why the shrine is known as Ajisai no Miya (Hydrangea Palace) as well.
