Ölfus municipality has many interesting hiking and walking trails, and everyone should be able to find something that suits them. The most popular trail is Reykjadalur valley, where you can bathe in a hot river.
Walking on the beach in Ölfus, surrounded by black sand, lyme grass, and the ocean, allows you to connect with nature and unwind from stress. Another beautiful option is Hafnarnes, the surroundings of the lighthouse in Thorlákshöfn. There you can walk around the cliffs, listen to the ocean and watch the surfers ride the waves.
On the road no. 39 there are a few hiking trails, two of them go up the mountains Litli Meitill(Small Meitill) and Stóri Meitill(Large Meitill), and from the top, you have breathtaking panoramic views.
The geothermal area around the dormant volcano Mt. Hengill is perfect for hiking. There are numerous marked hiking trails colored after difficulty.
https://www.on.is/en/environment/hengill-area/
For those looking for a full-day hike, walking on the cliffs from Strandarkirkja church in Selvogur to Thorlákshöfn is an excellent option. It's suitable for most if not all hikers as it is mostly on even ground, and the scenery is truly unique while walking on the cliffs. Be cautious while walking on the cliffs; if needed, there is a walking trail further from the cliffs.