As a big walker here’s what I’d recommend for an epic walk:

• Start in inner harbor near aquarium
• head east exploring the piers using the waterfront walkways/boardwalks/pedestrian bridges
• head east into harbor east and go up into little Italy
• weave southeast through fells point until you get to Broadway Square
• you can do some of exploring here. The loop of Thames St to Bond to Shakespeare is charming. Then head over to Pitango bakery and cafe on the water at St Ann and Fell St for lunch
• If time: walk up through upper Fells Point to Patterson Park, then head back to Fells Point toward the water
• walk back west on the waterfront boardwalk (green line on google maps) headed to Pier V. You can pick up the boardwalk in Fells Point in front of the Pitango on St Ann, or if you want a longer walk you can start the boardwalk a bit NE of there along the marina, starting at the eastern ends of Lancaster or Thames St, where they meet the water
• once you get to pier V you can take the free city water taxi over to federal hill and walk over to the commercial area along/between Light St and Charles St for dinner