RXJ1720.1+2638. Top left panel: high-resolution 144 MHz LOFAR image of RXJ1720.1+2638. The contour levels start at 3σ, where σ = 200 μJy beam⁻¹, and are spaced by a factor of two. The negative contour level at −3σ is overlaid with a dashed line. The beam is 14′′ × 9′′ and is shown in grey in the bottom left corner of the image. Top right panel: low-resolution 144 MHz LOFAR image of RXJ1720.1+2638. The contour levels start at 3σ, where σ = 330 μJy beam⁻¹, and are spaced by a factor of two. The negative contour level at −3σ is overlaid with a dashed line. The beam is 41′′ × 26′′ and is shown in grey in the bottom left corner of the image. Bottom left panel: optical Pan-STARRS image of RXJ1720.1+2638 with the high-resolution (14′′ × 9′′) 144 MHz LOFAR contours overlaid. The red circles indicate the cluster-member galaxies with available spectroscopic redshift. Bottom right panel: Chandra X-ray image of RXJ1720.1+2638 smoothed on a scale of 5′′ with the low-resolution (41′′ × 26′′) 144 MHz LOFAR contours overlaid. The red arcs indicate the position of the two cold fronts found by Giacintucci et al. (2014a).