The cliffs of Dover are shown almost pictorially on this plan, with dark striations indicating steepness. Relief is shown elsewhere by shading and interlining ('hachuring'). Field boundaries are observed. The sandy coast is represented by a speckled pattern and grassland by a green wash. Dover Castle is seen in plan, with dark hachure lines depicting the steep underlying rocks. The castle, known as the 'Key to England', was a site of unique strategic importance, affording the shortest crossing point of the English Channel to continental Europe. Its defences were improved during the Napoleonic conflicts. Special tunnels were even bored beneath the keep for emergency entrance and exit. This drawing was surveyed while the war was at its most ferocious, yet no batteries are recorded.