Island Grotta is the the point of the Seltjorn Peninsula of which the capital comprises the greatest part.  In earlier times a farm occupied the island and the lighthouse standing there was built in 1897.  It was restored thoroughly in 1947 and has been maintained well since then.  There were fishing outfits on the island as well, when the fisheries were based on open rowing boats. 

The volunteer rescue corps of the Seltjarnarnes community was named after one of the caretakers of the lighthouse, Albert Thorsteinsson (1910-1973).
The island is connected to the mainland by an isthmus, which is flooded during high tides, and many people walk across at low tides to enjoy the variety of the bird life and an occasional seal nearby.  The land has been and still is subsiding rather quickly and those who have lived in the community for a long time have witnessed the gradual advance of the sea.  In the immediate vicinity of the island is a popular golf course and a beacon for one of the runways of the Reykjavik Airport.