Field Agent Walmart has built a giant tower inside one of its stores that acts as a vending machine for online orders.

The tower — or automatic pickup machine, as it's called internally — is being tested in a Walmart store in Bentonville, Arkansas, not far from the company's headquarters, according to a person familiar with the matter.

The machine is so big that the company had to remove a chunk of the ceiling to fit it inside the store. It's located right inside the store's entrance.

We learned about the machine after the consulting agency Field Agent spotted it in the wild and sent us a tip.

Here's how it works: When a customer orders something online for in-store pickup, the customer gets an order number.

When the person arrives at the tower, he or she enters the order number into the machine. Then the machine spits out the customer's package the way a vending machine can do with a bottle of Coke.

The machine's giant size is due to the fact that it holds tons of packages inside. While it requires a lot of space, it's more versatile than pickup lockers — which Walmart has also tested — because it has the ability to adjust the size of the compartments where packages are kept, our source said.

Walmart said it was still gathering feedback from customers while testing the machine.

"We know speed and convenience are important to our customers, and we're always looking for new ways to bring it to them," Walmart spokesman Kory Lundberg said. "We are excited to be one of the first companies to test this new technology and are looking forward to hearing feedback from our customers and associates."