This mountain is located south of Osaka in the Wakayama prefecture. It’s known as the base of the Shingon Sect in Japanese Buddhism. This sect taught esoteric secrets that came from China and many samurais were practitioners of this early tantric teachings. Nowadays is a sacred pilgrimage site as well as a tourist attraction named as a UNESCO world heritage site.
Getting there it’s quite an effort since there are no direct trains. Your trip will start from the Osaka Namba station of the JR line, but actually the railway line that take you there is the Nankai Line. There you are able to buy a full round trip ticket, including train transfers and the lift to the top of the mountain. The trip takes around 3 hours, and you must be careful to leave early, since the place gets crowded very fast.
Once at the top of the mountain though, which lies at no more than 2000 meters above sea level, you will find as very typical in japan a full range of services, vending machines and a mini city. People still live there, so there are many houses, streets and even a bus line. Take 
the bus, as it’s a long distance from the entrance to the attractions.
The site offers a diverse range of things to see and to do. First starting by the old temples and Shrines. The most famous view of the mountain is the Danjogaran, a huge Pagoda like building that hosts a temple dedicated to the Buddha. It’s actually one of the few places in Japan that is forbidden to take pictures inside. Next to this shrine we can find 3 wooden buildings dating from the early 9th century. This structures were part of the Series of temple complexes built there including also a citadel with dorms and the administration of the temple.
All over the mountain top Shinto shrines and Buddhist temples scatter around in random order. The most famous temple in the hill is the Kongobuji temple, but most of them are really pretty and deserve a visit. In many of those temples you may find a place for burning offers and also people splatting water to 7 Buddha statues in their different positions, both characteristics of Shingon Buddhism.
Besides the temples and Shrines the mountain is also home to several cemeteries, some of them pretty new were nowadays some notorious people are buried, and others ancient graveyards where samurais warriors found their last resting place. In the new cemetery is interesting to find that big companies burry their long time employees in their own parcels… maybe as part of the job benefits for senior salaryman. Contrast between the mold covered old tombs and the new polished monuments is astonishing.
Also to be found there are the incredibly beautiful Ryokans, Japanese typical guest houses, as well as several places that are only for pilgrims. These places are quite expensive and really only for pilgrims so are not open to foreigners. Most of them though you can access and their gardens, gates and rooms are worth the visit.
The atmosphere at Koya san is definitely sacred and strolling through the old tombs, buildings and shrines is a wonderful fulfilling experience, worth the hassle of the trip there.
