Insects can traverse natural terrain filled with obstacles comparable to or larger than their body size. Understanding how their movement and behavior emerges from interaction with complex 3-D terrain is challenging, especially at large spatiotemporal scales. Existing terrain testbeds limit observations to small scales (~10 strides, ~10 body lengths) and low spatial resolution (~3% pixels representing the animal). Here, we used a recently-developed terrain treadmill to perform high-resolution observations of discoid cockroaches moving through large obstacles over large spatiotemporal scales. The terrain treadmill consists of a transparent outer sphere and a concentric inner sphere mounted with large obstacles and uses feedback control to keep an untethered moving animal on top. We studied how the animal traversed sparse and cluttered pillar obstacles. In a single trial, each animal moved on the terrain treadmill continuously for ~500 seconds (~2500 strides) covering ~50 m (~1000 body lengths), changing direction freely (as opposed to only forward movement on traditional treadmills). The higher spatial resolution (~10% pixels representing the animal) enabled us to reconstruct the animal’s 3-D motion in the terrain and estimate contact of its body and antenna with obstacles. For cluttered pillars, the animal almost always traversed by rolling its body into gaps and with body-pillar interaction. For sparse pillars, interaction reduced due to wider gaps and use of antennae to detect and avoid obstacles. Apart from walking and running, the animal displayed behaviors such as antenna sweeping, body rolling/turning, and pillar climbing. Our study established a new experimental system for measuring large obstacle traversal behavior with a high spatial resolution over a long duration and distance.