thumb|alt=Water on grassy lowland with hills in the distance.|View from the summit of Burrow Mump across the winter-flooded Somerset levels toward Aller Hill and the village of Aller, Somerset. Burrow Mump, an ancient earthwork owned by the National Trust, is a natural hill of Triassic sandstone capped by Keuper marl, standing at a strategic point where the River Tone and the old course of the River Cary join the River Parrett. It probably served as a natural outwork to the defended royal island of Athelney at the end of the 9th century.
thumb|alt=Water on grassy lowland with hills in the distance.|View from the summit of Burrow Mump across the winter-flooded Somerset levels toward Aller Hill and the village of Aller Somerset. Burrow Mump an ancient earthwork owned by the National Trust, is a natural hill of Triassic sandstone capped by Keuper marl, standing at a strategic point where the River Tone and the old course of the River Cary join the River Parrett. It probably served as a natural outwork to the defended royal island of Athelney at the end of the 9th century.