Benbow is the second of Ambrym's two main active volcanoes, sitting on the eastern side of the caldera from Marum. It tends to be more gassy and unpredictable, and is typically approached as a second day's hiking for those who have already done Marum.
The caldera traverse from Marum to Benbow crosses a surreal landscape of black ash, fumarolic ground, and occasional solidified lava flows. The distance is not great but the terrain is slow going and the altitude changes are significant.
Most guides offer multi-day trips that combine both volcanoes, sleeping on the caldera floor in basic camps. These overnight trips allow you to see both lava lakes and to experience the caldera at night — when the glow of the lava reflects off the gas clouds above the craters and the ash plain is lit an eerie orange.