Astola is Pakistan's largest offshore island at approximately 6.7 km long with a maximum width of 2.3 km and an area of approximately 6.7 km2. The highest point is 246 ft above sea level. Administratively, the island is part of the Pasni subdistrict of Gwadar District in Balochistan province. The island can be accessed by motorized boats from Pasni, with a journey time of about 5 hours to reach the island.
The earliest mention of Astola is in Arrian's account of Admiral Nearchos, who was dispatched by Alexander the Great to explore the coast of the Arabian Sea and the Persian Gulf in 325 BCE. The sailors in Nearchos's fleet were "frightened at the weird tales told about an uninhabited island, which Arrian calls Nosala".
The island consists of a large tilted plateau and a series of seven small hillocks (hence the local name "Haft Talar" or "Seven Hills"), with deep chasms and crevices, which are several feet wide. There are several natural caves and coves on the island. The south face of the island slopes off gradually whereas the north face is cliff-like with a sharp vertical drop.
Isolation has helped maintain several endemic life forms on Astola. The endangered green turtle and the hawksbill turtle nest on the beach at the foot of the cliffs. The island is also an important area for endemic reptiles such as the Astola viper . The island is reported to support a large number of breeding water birds including coursers, curlews, godwit, gulls, plovers and sanderling. Feral cats, originally introduced by fishermen to control the endemic rodent population, pose an increasing threat to wildlife breeding sites. E.g. the sooty gull (Larus hemprichii) had a major breeding colony on the island, now extirpated because of introduced rats.
Vegetation on the island is sparse and largely consists of scrubs and large bushes. There are no trees on the island. The largest shrub on the island is Prosopis juliflora, which was introduced into South Asia in 1877 from South America. There is no source of fresh water on the island and the vegetation depends on occasional rainfall and soil moisture for survival. Astola is also home to coral reef.
Astola island is a popular but "hard" destination for eco-tourism, although there are no lodging facilities on the island. Overnight tourists must camp on the island and bring their own provisions. Camping, fishing and scuba-diving expeditions are popular. It is also a site for observing turtle breeding. There has been some damage to Astola's ecology due to rats and domesticated cats left behind by fishermen, which have threatened bird nesting sites and turtle hatcheries.