Keri is a 3.1 hectare island in the Gulf of Finland. It is located about 6 km north of the island Prangli, and is one of the northernmost islands of Estonia. Keri has been situated by important seaways a long time and is the site of the notable Keri Lighthouse. In 1719 a lighthouse was erected there on the order of Peter the Great. The present lighthouse was built in 1803. During a well drilling in 1902 natural gas was discovered in the island. From 1906 to 1912 the gas was used to power the lighthouse and heat the other buildings on the island. During that time it was the only lighthouse in the world to be powered by natural gas. In 1912 after a seismic impulse the gas flow stopped.
The island has been inhabited only by the families of the lighthouse keepers. The last keeper left the island in September 2002. Since then the lighthouse operates automatically; the power is derived from a wind turbine and solar panels.