While today a generally flat and open landscape, in the Iron Age it was covered by bog, quicksand, and ponds, surrounded by dense woodlands. The road was at least 1 kilometre long and studies suggest that the timber used in construction was felled in late 147 BC or early in 148 BC. It is estimated that the sleepers alone amount to some 300 large oak trees, with a similar volume of birch for the rails. The Corlea Trackway ended on a small island, from which a second trackway, also dated to 148 BC and around 1km long, was connected to dry land on the far side of the bog. The construction of the roadway required a great deal of labour, comparable to that used in the construction of ritual monuments such as barrows. Gradually sinking under its own weight, it was covered by the bog within a decade of being built, where it remained preserved for two millennia.

The Corlea Trackway, was seemingly constructed in a single year and has suggested comparisons with the mythological tale Tochmarc Étaíne (The Wooing of Étaine). In the tale, Midir of the Tuatha dé Danann attempts to win back his lover Étaíne by completing a series of seemingly impossible tasks set by her husband, the High King Eochaid Airem. One of the tasks was to build a road across a bog where none had ever been before at a place called Móin Lámraige. To complete the task, Midir enlisted the help of a magical host of workers to build the road in a single night, but as they worked they sang a song which foretold that their burdensome task would, at the last, be flawed and lost to time.