By car you can drive from Reykjavik (30min) and then you are entering the west side of South Iceland and visiting attractions like Hveragerdi, Thingvellir National Park and Selfoss.You can enter South Iceland straight from Keflavík via Grindavík road (nr. 43) and the South Coast Road (nr. 427).You can also enter South Iceland from East Iceland visiting attractions like Hofn, Skaftafell and Jokulsarlon Glacier Lagoon.
By air is possible to fly to Hofn in Hornafjordur with Eagle Air and from there drive to the west through South Iceland to Reykjavik.
By bus you have a lot of possibilities, day tours, ordinary tickets and passports from the two companies with schedules in South Iceland.