Akechi Castle is located in Akechi-cho in Ena Gifu Prefecture. Akechi is the supposed birthplace of the famed Akechi Mitsuhide. The castle at Akechi is ruins and there isn't anything remaining. There are sign posts along the way with information in both English and Japanese that explain the history of the castle and surrounding area of Akechi. From the castle ruins you get a nice view of Akechi primary and Akechi middle school.
Azuchi Castle was one of the most important castles in Japanese history. It has since been destroyed and all that is left are some walls. But the hike around the mountain and the attached museum and shrine are more than worth visiting. As you hike up and around the mountain, you can learn about Oda Nobunaga, one of the greatest warlords in all of Japanese history.
Byoubuzan is situated in Mizunami. On the walk you can see great waterfalls and stunning views of rural Japan.
Cape Irozaki is part of the Fuji-Izu-Hakone national park and has some of the best views of the Izu coast. It is the most southern point of the Izu Peninsula.
Chiiwakyo is one of the coolest natural places in Aichi Prefecture. The hike takes you past some waterfalls, forest and caves. It's kind of way out in the sticks, but worth it.
Dogashima is one of the most famous area on the Izu Peninsula and part of the Fuji-Izu-Hakone national park. Dogashima has interesting rock formations and if the weather is good you can take a boat into the sea cave. It is also home to a land bridge that appears during low-tide which is pretty cool.
Fukuurajima is an island that you can reach from the Japanese mainland via bridge. Matsushima is considered to be one of the 3 views of Japan. The bay is littered with small islands that house unique vegetation. Fukuurajima itself is one of those islands. It has been designated a prefectural park and is protected. On the island you can view the unique plantlife and get some views of the Matsushima Bay. For the best view of the bay, I recommend taking a boat tour.
A hike up Mount Inari through thousands of Torii gates part of one of the most famous temples in Japan.
Gohou no Taki is a series of seven waterfalls located in Yaotsu in Gifu Prefecture. In the mid-1500s, the waterfalls here were used as a special training site making them also historically important.
A nice hike up Iwamura Castle with sweeping views of the Gifu countryside. Lots of history.