Bisitak 5559, kokapena 112
Nondik gertu Hveragerðisbær, Suðurland (Lýðveldið Ísland)
Start from the parking lot at Sleggjubeinaskarð and head back on the tarmac towards the main powerplant. Soon after take a right and follow the road up the hill. Its quite steep but since it is on tarmac not too difficult. Once at the top leave the tarmac at the first junction and follow the trail eastwards around the mountain (Skarðsmýrarfjall). There comes one hill which you have to hike up but from the top its nice easy flowing into Innstidalur along an old jeeptrack.
For the last bit (Sleggjubeinaskarð) drop the saddle and enjoy the steep somewhat technical descent back to the parking lot. :)
All in all a nice little track which can be cleared in about 1 - 1,5 hours.