Fiery Furnace, Slot canyon in Arches National Park, Utah.

Fiery Furnace is a slot canyon network in Arches National Park with narrow passages between towering red sandstone walls that twist and turn unpredictably. The maze-like layout means walkers often need to navigate tight sections and squeeze through rocky passages to reach different areas.

Water erosion and wind carved these passages through red sandstone layers over millions of years, shaping the canyon system visible today. The same forces continue working slowly on these rocks.

The name refers not to heat but to the glow-red colour of the exposed sandstone, especially at sunset. The area lies where the collapsed Salt Valley and Cache Valley anticlines meet, and its shade keeps pools and puddles longer than the surrounding land, drawing mule deer that move about with little fear.

Permits and ranger-guided tour tickets are issued only at the park entrance visitor center; a self-guided permit requires watching an orientation video. Two trails lead in from the parking lot, but inside there are no maps, signs or markers, and the sandy washes and sandstone surfaces are the only routes. The guided tour covers about 2 mi (3.2 km) in roughly three hours over uneven ground, drop-offs and narrow passages. A viewpoint lies about 100 m from the parking lot, east of which the area begins.

The rock walls glow in deep red tones when the sun is low in the morning and evening. This happens because sunlight bounces off the canyon walls and the narrow space intensifies the colors.