The city that was to have the most influence on Marten van Heemskerck was Rome. He was very interested in the ruins left from the time of the Ancient Romans. He made many drawings of the ruined buildings and other things that he saw. His sketchbooks, which are now in a museum in Berlin are very important evidence for showing what Rome was like in the 1500s. One important building that he drew was St. Peter's Basilica which had been begun, but never completed.