The Sea of Sand is the caldera floor that stretches between the caldera wall and the volcanic cones — a flat, grey, ash-covered desert 10 kilometres across at its widest. Walking or riding across it is the practical requirement for reaching Bromo's crater stairs; it is also an experience in itself. On horseback from the saddle rental point, the crossing to the Bromo stairs takes about 20 minutes; on foot, about 40.
The experience at ground level is unexpected. The scale becomes clearer than it is from above; the cones are much larger than they appear from the viewpoint, and the flat grey expanse gives the whole scene a post-apocalyptic quality. In the early morning, before jeep traffic stirs up the dust, the light on the grey sand and the steam from the crater is atmospheric in ways the photographs don't quite capture. Horse rentals are available at the caldera edge; prices are negotiable.