Derby square and the site of the castle are still on the high point of the lad for the best vantage point, sloping down in all directions. Both Church Street and Lord Street slope down quite steeply to the old Pool and inlet along the course of Paradise Street, where you walk on level ground, but still above the old river bed.
Go with a map of old Liverpool if you're not familiar. Its a weird feeling and gives you a real new perspective on the layout of the Town, and how little the basic structure has changed.