Shopping on the Ecuadorian border
Tumbes is a chaotic border town. It’s about half an hour to the international bridge that separates Peru and Ecuador.
There is a free trade zone where you feel like you’re in Ecuador, but you don’t have to go through customs and nobody asks for your passport.
Just like Ecuador, you can buy things with USD. You can also get Ecuadorian food, like the traditional plantain with cheese: maduro con queso.
Tumbes is a 5 hour drive north of Piura. It does have an airport TBP but flights there are limited.