Rosenli is a beautiful recreational area close to the city. It would take you 20 - 25 minutes to get there by foot from downtown. Or you could go by bus no 4A or 4B to the end stop; a roundabout by the buildings on top of the hill. NB check that the bus is marked "Rosenli", or you would end up on the other side of the city ;-) From the roundabout walk between the tall and the lower buildings and you will find the walkway that ends where the two people are. See the linked map and / or check my "things to do" tip about hiking / biking close to the city.
There is a nice walking / biking path here, barbeque areas, lawns excellent for sunbathing and a couple of snug beaches. The path continues to Godalen along Gandsfjorden (towards the photographer), another, or should we say the same, nice recreational area. You could go directly to Godalen by bus no 6.