The colourful, sulphurous mud hole Leirhnjúkur is Krafla's prime attraction. From there you can meander round the Krafla Caldera , where several different lava flows overlie each other; some from the 1984 eruptions are still smoking.
Nearby Stóra-Víti is a 320m-wide explosion crater and lake (now inactive…allegedly). The 30-megawatt Kröflustöð power station sources steam from 17 boreholes around the volcano; step into the visitor centre for an explanatory film. One of the power station's preliminary searches produced the whopping crater Sjálfskapar Víti (Homemade Hell; near the Krafla car park) when a team drilled into a steam chamber, which exploded. Bits of the rig were found 3km away.
Between 18 June and 31 August, a bus runs from Reykjahlíð (outside the tourist office) to Krafla (Ikr1400) at 8am and 11.30am.
