Oslofjord

The Oslofjord is not a true fjord in the geological sense but a long drowned rift valley, about a hundred kilometres from the capital to the Skagerrak, narrowing at Drobak where the channel is only a few hundred metres wide and widening into open water further south. Its shores hold the densest concentration of summer houses in Norway, and its islands, several thousand of them, are where people from Oslo, Drammen and the Vestfold towns spend July. Public ferries serve the inner islands from Oslo year-round, and the coastal path network runs along much of both shores. The water is shallow and warms faster than the western fjords, which is why swimming here is a real season rather than a dare.

What you actually see

• The island archipelago - thousands of islands and skerries along the fjord.
• The narrows at Drobak - the channel where the fjord pinches to a few hundred metres.
• The summer towns - Drobak, Son, Tonsberg and Sandefjord along the shores.
• The public ferries - year-round boats to the inner Oslo islands.

When to go

June to August for swimming, boating and the full ferry timetable; the water peaks around twenty degrees in a warm July. May and September are good for the coastal paths without crowds. Winter reduces services sharply and the inner fjord sometimes freezes.

Honest expectations

The fjord is heavily developed along much of its shore, with private summer houses limiting access in places, though the shoreline itself is legally open. Boat traffic is dense in July. Water quality varies and jellyfish are common in late summer.

Nearby

Drobak and the Oscarsborg island lie mid-fjord; Tonsberg, Norway's oldest town, is on the western shore.