WThe Batu Islands are an archipelago of Indonesia located in the Indian Ocean, off the west coast of Sumatra, between Nias and Siberut. The three primary islands, of approximately equal size, are Pini, Tanahmasa, and Tanahbala. There are forty-eight smaller islands, of which the largest are Sipika, Simuk, Bodjo, Telo and Sigata; less than half are inhabited. The total land area of the seven administrative districts is 1,201.1 km2. The islands are governed as a part of South Nias regency within North Sumatra province. In Indonesian and Malay, batu means rock or stone.
WLake Sidihoni is a lake located within Samosir Island which itself is an island within Lake Toba, in North Sumatra, Indonesia and is therefore notable for being a "lake on an island in a lake on an island". It is approximately 11–12 km to the east of hot spring pools at Pangururan.
WMt. Sibayak is a stratovolcano overlooking the town of Berastagi in northern Sumatra, Indonesia. Although its last eruption was more than a century ago, geothermal activity in the form of steam vents and hot springs remains high on and around the volcano. The vents produce crystalline sulfur, which was mined on a small scale in the past. Seepage of sulfurous gases has also caused acidic discolouration of the small crater lake.
WNias is an island located off the western coast of Sumatra, Indonesia. Nias is also the name of the archipelago of which the island is the centre, but also includes the Batu Islands to the south-east and the small Hinako Islands to the west. Nias Island covers an area of 5,121.3 km2 (1,977.3 sq mi). It is mostly a lowland area rising to around 800 m (2,600 ft) above sea level. There were 756,338 inhabitants on the island at the 2010 Census; at the 2015 Census this had risen to 798,506.
WMount Pangulubao or Pangulubau is a mountain near Lake Toba in Sumatra.
WSibolga Bay is a natural harbour on the west coast of North Sumatra, Sumatra, Indonesia. It is named after the city of Sibolga which is located inside of the bay.
WThe Sipiso-piso is a plunge waterfall in the Batak highlands of Sumatra, Indonesia. It is formed by a small underground river of the Karo plateau that falls from a cave in the side of caldera of Lake Toba, some 120 metres (390 ft) down to lake level. Sipiso-piso is a well-known tourist attraction and a nearby vantage point offers views of the falls and lake.
WLake Toba is a large natural lake in North Sumatra, Indonesia, occupying the caldera of a supervolcano. The lake is located in the middle of the northern part of the island of Sumatra, with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2.88°N 98.52°E to 2.35°N 99.1°E. The lake is about 100 kilometres long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world. Lake Toba Caldera is one of the twenty Geoparks in Indonesia, which is recognised in July 2020 as one of the UNESCO Global Geopark.