The area around Lake Toba in North Sumatra, Indonesia is predominantly Christian rather than Muslim and you can see many lovely Batak Christian churches on the banks of the lake like this one.
The Huria Kristen Batak Protestan (HKBP), which translates into the Batak Christian Protestant Church, is the largest Protestant denomination in Indonesia, with a baptized membership of 4,178,256. Its present leader is the Ephorus (or Bishop) Rev. Dr.Bonar Napitupulu.
It was founded in the 1880s by Dr. Ludwig Ingwer Nommensen, of the German Rhenish Missionary Society, who worked in the District of Tapanuli in Tarutung, North Sumatra. In 1930 it became the first independent self-governing Christian body in what was then the Dutch East Indies. Tarutung and the Batak region remain the stronghold for the HKBP in the mainly Muslim nation of Indonesia, although worshippers are found throughout the country.
Batak is a collective term used to identify a number of ethnic groups found in North Sumatra, Indonesia. The term is used to include the Toba, Karo, Pakpak, Simalungun, Angkola and Mandailing, each of which are distinct but related groups with distinct, albeit related, languages and customs. Occasionally it is also used to include the Alas people of Central/Southern Aceh, but usually only as relates to language groups.