IT could be the cobblestones, the narrow winding streets or the majestic main square.
It might be the proximity to the Sacred Valley and the Inca Holy Grail that is Machu Picchu.
Whichever it is, Cusco is the kind of endearing city you never want to leave.
Its mystery and charm weaves a web so tight around your heart you'll be talking about it for years.
Arequipa and Chivay had already given a taste of what was to come but seeing so many people in traditional costume makes you feel like you've stepped back in time.
Pop around a corner and you might see a woman with her llama.
Sometimes they'll ask you for money in exchange for a photo which makes it all seem less genuine.
But many of them are the real deal.
There are artisans walking around with gorgeous landscape and scene paintings in oils and water colours.
It's free to look and there are some amazing works for the wall back home.
The handicrafts market is less impressive, with factory-made textiles dominating the selection rather than the genuine hand woven goods.
But you can find a store selling solely genuine alpaca and sheep wool weaves near by.
They even have photos of the creator, their name and age.
But you can find great, genuine, pieces on the Lares Trek or in La Paz in Bolivia for about half the price, and slightly less quality.
Seeing women, and some men, spinning wool and weaving the traditional way with bones and pieces of wood is an eye opener.
You could never buy a factory-made textile after seeing the work that goes into a genuine piece which can take weeks or months because they are usually secondary to other household chores.
There are important Inca ruins in the hills just above Cusco which are walking distance, or accessible by horse for something different.
The nearby Sacred Valley is gorgeous with its picturesque mountains, many with terraces for agriculture on their steep slopes.
You can find people who weave, make chocolate, do pottery and many other crafts the traditional way.
The true beauty of the valley is Ollantaytambo which has an important place in Inca history thanks to many a battle with the Spaniards from Cusco to the sacred town.
Ollantaytambo is also perfect for meandering the streets and the easily accessible ruins on the surrounding hills.
Cusco's other charm is the fabulous food and nightlife.
Start with dinner at Nana Raymi, which has great Peruvian fare, or Fallen Angel, which has bathtubs of fish under glass as tables and offers a delicious cocktail list.
Then head to The Shot Bar and choose a few shooters from the huge blackboard of options.
The flaming shots, lit with an oxy torch and drunk lightening fast through a straw, are a fantastic start to the evening.
Drop into Mushrooms, on the corner of the main square on the second floor, for another drink and some 80s classics.
Then head to The Lek or Mythology on another corner of the square for a mix of Latin and modern Western tunes to dance the night away.
Mythology will let you dance on the bar if you feel like a wild night.
There is also another good club above the Indian restaurant just off the main square which will take music requests.
You are sure to have a night to remember in Cusco.
A Latin Affair is a travel column written by Rae Wilson.