sentences:  Víðgelmir
  
  Víðgelmir is a lava tube situated in the Hallmundarhraun lava field (formed around 900 AD) in west Iceland, around 2 km southeast of Fljótstunga farm in Hvítársíða, Borgarfjörður.The roof of the lava tube has collapsed, creating two large openings near its north end which are the only known entrances.