Near J-List there’s a park I used to frequent with my kids which had two small hills in the center. They weren’t actually hills, but kofun (burial mounds), miniature pyramids containing the remains of feudal lords which were built from 250 ~ 590 A.D., before the mainstream arrival of Buddhism and kanji writing from Korea and China. There is a staggering number of these burial mounds around Japan — more than 161,000 — but since Japan had no writing system in those days, next to nothing is known about the civilization of the mound builders apart from baked clay statues of soldiers and horses they included in the tombs. Since these burial mounds are protected areas, it makes sense to locate parks for public use around them, both as a logical way to make use of available land and also to bring people into contact with their ancient past. Whenever it snowed I’d take a day off from work and take my kids to the park so they could slide down the graves of their long-dead ancestors on a sled. It was great fun.
There are many burial mounds in Japan.
