With that height, I’d think Allium ‘Gladiator’ or Allium ‘His Excellency’.

Generally resembles various culinary alliums.

Could just be a leek.

Grocery store scallions I grew out ended up just like that: white globes about the same size on 4' stems. They started out the diameter of a pencil but have wintered over twice and each time got much thicker and a bit taller. There really is no way to know just exactly which variety you have or even whether culinary or decorative. It could even be the base of some picnicker's salad scallion discarded, and then rooted it self out. The leeks known as "elephant garlic" have also naturalized in quite a few places, they have flat leaves, if this has round hollow leaves that points to the onion side.