The islands of the Oslo fjord

Since 2000 the Kavringen light has held Oslo's time capsule, a titanium container due to be opened in the year 3000. A lighthouse on a bird reserve is the city's letterbox to people a thousand years ahead.

Norway's first airport lay out here on a grazing island, and it could only be used in summer. When the fjord froze, the flying stopped, which is why Sola and later Fornebu took over.

Before the cabin owners came, this was an island for sick children. The sanatorium ran from 1885 to 1926, treating glandular tuberculosis with fresh sea air.

The grass people picnic on sits on top of more than 45 years of Oslo's household waste. The sand was trucked in; the ground beneath it is the city's own history in compressed layers.

The pine forest here grows on lime-rich ground, which gives it a flora you do not find everywhere. The calcareous pine forest on Rambergøya counts as one of the best preserved on the whole island chain in the inner fjord.

The cabin town began as tents around 1905. A midsummer party with dancing around 1920 triggered the first restrictions, and eventually the arrangement that produced the 289 cabins.

Long before the cabins, an optical telegraph stood here, built in 1809 to pass word on about enemy ships heading for Akershus during the Napoleonic Wars.

The rock here is an open book of geology. Trilobites, corals and graptolites sit in the smooth bedrock from a time more than 400 million years ago, when the area lay under a shallow tropical sea south of the equator.

Ulvøen Rundt is an open-water race around the island, revived in 2014 with 54 swimmers. The distance is 2,250 metres, and the fastest came round in 33 minutes.