The following morning is spent in the company of Irene Levy Baker, author of 100 Things To Do In Philadelphia Before You Die and Unique Eats and Eateries of Philadelphia. She’s a Philly-expert and human dynamo and, like yesterday’s guides, remarkably thin in the face of citywide temptation. It is, however, a brilliantly walkable city – thanks to William Penn, it was the first US city to be built in an easily navigable grid system – which is probably just as well.