Seismic images of staircase layers at the bottom of the Mediterranean Undercurrent with a lateral coherence up to 50. km and a horizontal resolution of ~10m are presented. The images show clearly the interaction between these staircase layers and other flow structures such as meddies, seamounts and internal waves. The staircase layers were imaged during two different surveys that used different sound sources. Comparison between seismic images and historical oceanographic observations illustrates the importance of using a seismic source adapted to the vertical scale of the oceanographic target to be imaged. Wavelengths larger than the size of the staircase structure distort the image in the vertical. For optimal imaging, deconvolution of the data is required

Consejo Superior de Investigaciones Científicas is funding the first author's work by means of a JaeDoc contract. This work has been supported by the “Grup de Recerca de Catalunya 2009 SGR 146”. Finally, we want to thank Barry Ruddick for his thoughtful and careful review that significantly improved the paper##

9 pages, 12 figures, 2 tables

Peer Reviewed