From 57 BC to 668 AD, three kingdoms, Baekje, Goguryeo, and Silla, dominated the Korean peninsula. The Baekje controlled the western part of what is today South Korea. Its base was South Chungcheong province, with its capital at its peak (538 AD to 660) in Sabi, 2 kilometers away from Buyeo. In the 300’s, Baekje expanded north, all the way to the modern-day Chinese border, but it remained confined to the West.
Having control of a long coastline, it became a sea power, exporting products and culture to Japan. According to the 8th century Japanese books Nihon Shoki and Kojiki, Chinese characters were brought to Japan by the scholar Wani, sent by the King of Baekje during the 5th century (stories that are difficult to verify).
While very little remains of the Baekje, the Buddhist temple in the middle of Yeobu, Jeongnimsa, contains excavated and reconstructed ruins, and the royal tombs, seven mounds where a king of the Sabi era and his family were buried, are built on a mountainside next to the city wall. (Taxi costs 6,000 Korean won.)
More tombs and relics are located in Gongju city, north of Yeobu, but I only visited Yeobu on this trip.