The second stop on our 3-week Peru adventure was Cusco, headquarters of the Inca Empire and gateway to Machu Picchu. We set up base camp for the next eight days since numerous other excursions we had scheduled began here.

The city sits at an altitude of over 11,000 feet above sea level. We expected chilly nights and packed accordingly. High altitude also meant thin air, but since we live at 8,400 feet and do cardio several times a week at the gym we thought, “No problem breathing there for us.”

Wrong.

Somehow our research overlooked the fact that while the historic downtown area is relatively flat, the surrounding neighborhoods rise up dramatically.

And in the area where we were staying, the sidewalks and streets are perilously narrow. Walking at night was not a relaxing stroll.

When we returned to our Airbnb the first evening after going down, down, down one of these former donkey paths to dinner, Cynthia became so winded on the way back up we had to stop at a hotel to let he...