The lee side of the islands Sletter, Eldøya, and Kollen south and west of Larkollen was an easily accessible harbor no matter the wind and was also was easy to defend.
On the island Eldøya a settlement was established including an inn, which according to tradition today still stands after being moved to a location north in Larkollen in the 19th century.
In the early 20th century Larkollen, which today is known as a sleepy suburb for Moss, became a prime summer destination for well-to-do families from Oslo and Fredrikstad.
He built his summer house just north of Larkollen in the 1880s, just after the railroad was opened between Christiania and Fredrikstad, with a station at nearby Dilling.
A moraine from the last ice age surfaces on the coast of the island Kollen in the north and follows the shoreline south of Rørvik to the island/peninsula Danmark on the northern side of the Kure fjord.
The terrain of Kollen and Danmark and part of the beaches are dominated by large sand and water-scoured moraine rocks that have been moved by the glaciers.
On Kollen, Eløen and the Sletter islands to the south, volcanic rock comes up to the surface, as a rhomb porphyric conglomerate, part of the unique Oslo graben.
A 9-year-old's life on the island Kollen in the post-WW2 year 1945-46 has been described in an autobiographic children's book by Astrid Karlsen Scott, "Little House on the Fjord", published by Nordic Adventures Inc. in 2004.
King Olav often sailed his boat "Sira" from Hankø on day trips to Larkollen and back in later years.
John Forbes Kerry, democratic candidate in the US Presidential Election in 2004, visited Larkollen several times as a teenager in the years from 1959–62, when his family lived in Oslo.