Sunlight is Earth's primary source of energy. The other significant source of Earth's energy is the store of fissionable materials generated by the cataclysmic death of other stars. These fissionable materials trapped in Earth's crust give rise to geothermal energy, which drives the volcanism on Earth and also makes it possible for humans to fuel nuclear reactors. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight.

Mount Penanjakan (2,770m), its peak also called Viewpoint #1, located just north of the caldera, is a mountaintop viewpoint accessible by paved road from Tosari and hence popular with jeeps and even tour buses. At the peak lies an antenna array (easily spotted from miles around), many shops, a mosque and several "real" buildings. It's the highest point easily accessible, so many visit here to get a good look around. The most popular sight is the sunrise: most of the crowd comes to see the dawn at 05:00 and you will likely have the large concrete observation post to yourself if you arrive later in the day. A steady hike from Bromo to Batok and then around the rim to Penanjakan will take about three hours and the last ascent of about 500m is very stiff indeed but truly worthwhile. Ancient Javanese Hindu texts tell of how Bromo-Penanjakan-Semeru (or Mahameru as it was then) was the spiritual axis of the universe and the point of all creation. The view from Penanjakan will explain why - it is truly breathtaking. This is where most of those iconic picture postcard views are taken from. After you have had your fill of the views, a hike back across the sea of sand to Cemoro Lawang will take about 2h.

Sunlight is Earth's primary source of energy. The other significant source of Earth's energy is the store of fissionable materials generated by the cataclysmic death of other stars. These fissionable materials trapped in Earth's crust give rise to geothermal energy, which drives the volcanism on Earth and also makes it possible for humans to fuel nuclear reactors. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight.