This is the starting point for a popular hiking trail near Reykjavík, known as Mt. Esja or Esjan. The trails are frequented by both locals and tourists and hiking here provides rewarding views over the city and surrounding landscapes. If you're looking to fill some time while in the area and the weather is nice, this hike is a good idea.
There is a hiking center at the trailhead - check-in here to determine which trail is best suited for you, your time, and the weather.
Note: hiking in the winter when trails are covered in ice and snow is not recommended.