We tried Walmart's massive online pickup tower - and it shattered our expectations

Walmart is building giant self-service kiosks that retrieve customers' online orders in its stores.

The kiosks, which Walmart calls pickup towers, are in about 20 stores today. Walmart is planning to roll them out to more than 100 locations over the next couple of months.

We recently tested one of the towers at a Walmart store in Midlothian, Virginia, and we were shocked by how easy and quick it was to use.

The last time we reviewed Walmart's in-store pickup service for online orders, we were underwhelmed. The pickup counter was inconveniently located in the back of the store, and the entire process took half an hour.

This time, we were in and out of the store in under a minute.

To test out the tower, we ordered several items on Walmart.com and selected in-store pickup. A couple of days later, we got an email from Walmart saying our order was ready.

When we arrived at the store, we found the pickup tower a few steps from the entrance. Its sheer size made it easy to spot - it's staggeringly large, standing more than 16 feet tall and 8 feet wide.

When we approached the machine, we were prompted to scan a barcode or enter an order number. We chose to scan the barcode that was included in our email from Walmart.

Within five seconds of scanning the barcode, a previously hidden compartment above the screen lit up, revealing a conveyer belt and a cardboard box that was seemingly produced out of thin air.

Then a glass door retracted, giving us access to the box.

That was all there was to it.

Walmart has said the pickup tower retrieval process should take 45 seconds, so we were shocked that in reality, it lasted under 10 seconds.

Upon retrieving our items, we left the store. It was the easiest and most convenient Walmart experience we've ever had.

It's easy to see why the company is ramping up the rollout of these towers to more stores, but the tower does have its limitations. It can only hold small- to medium-sized boxes, and it doesn't have any refrigeration capabilities for items like groceries.

For groceries, Walmart is testing a much larger machine with internal freezers and refrigerators. If that machine is as easy to use as the pickup towers, it will be a game changer for Walmart's grocery business.