The flat-topped basalt massif that rises north of Reykjavik is the capital area's favourite mountain hike, and Mosfellsbær is the natural starting point. The standard trail begins at the Esjustofa visitor centre at Mógilsá and climbs through birch scrub to a series of waymarked stopping points: Steinn at 597 metres is where most casual walkers turn back, while those continuing to the summit cairn at Þverfellshorn (780 metres) tackle a short chained scramble at the top.
Allow three to four hours round trip in good weather. The views from anywhere above the treeline take in the whole of Faxaflói Bay, the Snæfellsnes peninsula on a clear day, and the rooftops of Reykjavik to the south. The trail is doable year-round but in winter you need crampons or microspikes — the upper slopes ice over fast. A bus from Reykjavik runs to the trailhead in summer; in winter you need a car or taxi.