The waters of the Oslofjord to the south and the forested hills of the Nordmarka inland to the north are immensely popular for everything from boating and hiking to skiing, and on all but the shortest of stays there's ample opportunity to join in. The island beaches just offshore in the Oslofjord and the open forest and ski jumps at Holmenkollen are obvious targets, both within easy reach by ferry or underground train. Oslo curves round the northernmost point of the Oslofjord, which extends for some 100km from the Skagerrak, the choppy channel separating Norway and Sweden from Denmark. As Norwegian fjords go, Oslofjord is not particularly beautiful, but amongst a string of workaday industrial settlements is Norway's only surviving fortified town, Fredrikstad, with its angular bastions and grid-iron of late sixteenth-century streets; it's best visited as a day-trip by train from the capital. Oslo curves round the northernmost point of the Oslofjord, which extends for some 100km from the Skagerrak, the choppy channel separating Norway and Sweden from Denmark. As Norwegian fjords go, Oslofjord is not particularly beautiful, but amongst a string of workaday industrial settlements is Norway's only surviving fortified town, Fredrikstad, with its angular bastions and grid-iron of late sixteenth-century streets; it's best visited as a day-trip by train from the capital.