Bristol Backyard Ultra takes place on the woodland and parkland trails of Blaise Castle Estate in Bristol. The 4.167 mile (6.7km) loop is fully marked and easy to follow, but runners should expect a genuinely challenging course featuring hills, uneven terrain, roots, rocks and a steep downhill section that becomes increasingly demanding as the hours pass. With approximately 160m of elevation gain per lap, this is a tougher and more technical Backyard Ultra than many traditional road or gravel-based formats.