I´ve found the most noticeable thing when you travel is the different smells. Cusco is certainly no exception.
Apart from the obvious difference in the air that comes from it being an entirely different country on an entirely different continent, walking up and down the tiny cobblestoned streets, avoiding tiny cars hurtling towards you at break neck speeds, you walk in and out of pockets smells.
Some are delicious like boiled corn on the cob or some strange spicy dish. Some are not so delicious - The sewers are open air so the pungent smell of human shit will also hit you when you turn a corner occasionally and when it started raining, all the urine from the people who piss in the streets started running down the hill and the smell rose up from the ground.
Occasionally I smell sweet whiskey or a flowery jasmine smell. Smoke and diesal from the pocket sized taxi cabs filled full of pocket sized people; they really are tiny, tiny people. The women wear fedoras and alpaca sweaters; their thin brown legs look like they are wooden sticks peaking out from under their very wide and colorful skirts that come up to just above the knee. Some of these tiny indigenous women lead Alpacas, hoping that you will take your picture with them for a few soles. The Alpacas have a woolly dusty smell and a very soft eye with long lashes.