Tamon Castle was built by Matsunaga Hisahide between 1559 and the following year. Situated on Mt. Mikenji (present-day Horen-cho, Nara City), this hirayamajiro-style castle (a castle built on a low mountain in an area of plains) is estimated to have measured approximately 100 meters east to west and 100 meters north to south. Mt. Mikenji, which later became known as Mt. Tamon, was an ideal base from which to assert control over Yamato Province. For example, overlooking Todai-ji Temple and Kofuku-ji Temple below, it allowed Hisahide to control the Kyoto Kaido Highway that connected Kyoto and Nara. With purported features including a four-story turret, equivalent to what later became the castle tower, and an elongated turret set out like a tenement house, later called the Tamon Turret, the castle is considered to be a pioneer of early modern castle fortifications.

In 1580, Tsutsui Junkei of Tsutsui Castle was granted Koriyama Castle by Oda Nobunaga. He had large rocks brought over from the now abandoned Tamon Castle, and called in carpenters from all over Nara to begin construction of the castle. It is said that Akechi Mitsuhide also came to inspect the castle’s construction at this time.

Uda Matsuyama Castle was built around the middle of the 14th century by the Akiyama clan, one of the three generals in Uda. Located on top of a 473-meter (roughly 1,551 feet)-high mountain, the castle’s remains reveal the existence of a castle tower. The castle was located in an ideal location overlooking the eastern part of the province, and together with Koriyama Castle and Takatori Castle, it played a key role in the control of Yamato Province under the Toyotomi administration. The lord of the castle changed frequently over a short period of time, but decorative ridge-end tiles bearing the family crest of the Taga clan have been excavated here, suggesting that the castle was extensively renovated during the reign of Taga Hidetane, who held the castle for eight years.

Shigisan Castle was built by Kizawa Nagamasa in 1536. Located at the top of Mt. Shigi (Odake), 437 m above sea level, it was a typical mountain castle of the Sengoku period, and functioned as a base for ruling over Yamato Province by controlling the road over the Shigi Mountains. The castle extends approximately 700 meters from north to south and 550 meters from east to west, making it the largest mountain castle in Nara Prefecture.
In 1542, Kizawa Nagamasa was defeated in the Battle of Taihei-ji, and the castle was burned down. However, Matsunaga Hisahide, who moved into Yamato Province, renovated it in 1559, building a large-scale fortress.

Takatori Castle was built in 1332 by Ochi Kunizumi, a member of a powerful family belonging to the Southern Court, as a branch castle of Kaibukiyama Castle. At first, it was a small castle with a simple moat and earthen mound, a type of castle typically seen in medieval Japan. Later, however, it was substantially remodeled by Honda Toshihisa, a vassal of Toyotomi Hidenaga, and others, and was reborn as an early modern castle. With a relative elevation of 390 meters (difference in height from the foot of the mountain to the main enclosure), it is the highest of its kind in Japan, and is one of the three great mountain castles in Japan, along with Bitchu Matsuyama Castle in Okayama and Mino Iwamura Castle in Gifu. The castle’s perimeter is estimated to be about 30 kilometers, and the perimeter of the bailey (inside the stone walls) about 20 kilometers, which is equivalent to the size of Himeji Castle.