There’s many an ancient temple or castle to see in Japan, but most are recent, concrete reconstructions. Better than nothing but ruins it for me.
The oldest intact interesting items are in Asuka, 1 hour by train from Osaka, and I’m guessing the same distance from Kyoto.
Even if you don’t like ancient things, it is still awesome.
The shrines, temples and tumuli are quite spread out, in all corners of this small town. It took me 3 hours to see half of them. On bicycle.
The town isn’t picture perfect, it isn’t tarted up for tourists. There are no restaurants with English signage. It is a working town with schools and gas stations and rice paddies. But the landscape is quintessential Japanese, with big beautiful leafy trees, creeks, small hills, little veggie patches, cute houses, narrow alleys and front yards with 5 foot bonsai trees.
You get to see a lovely rural town and regular Japanese life from a bicycle (300 yen per hour). The bike paths are excellent and mostly flat. You might encounter the odd tour bus but mostly there are a handful of people at each “attraction”.
Most are free. Otherwise little old ladies tick boxes on ledger pads. This is not a commercial operation at all.
The top image is the Tortoise Stone. Basically everything here dates to around 700AD.
These are two out of three parts of a stone chamber that was once in a mound. The top fell off and ended up 100m downhill.
And this is the best of the ones I saw. You don’t need to go to Bolivia to marvel at perfectly fitting giant boulders. Try and do this at home without machinery… This tumulus is on quite a big mound, with surrounding moat. 
I always deliberately not do something when visiting places I like. Checkout this insane carved rock that’s a bit like a spaceship.
http://benotdefeatedbytherain.blogspot.com/2014/06/the-ancient-rock-ship-of-asuka.html?m=1
A reason to return…