Riddle: Vegtable, not mineral

Don't Mistake with the itching red scab

Hated upon by most children I am

Planted in gardens, and then I will wake

Third letter with alphabet, number 19

What am I

Riddle: What Building?

Here's my riddle (It isn't hard):

Belgium is an England away, but I can't see that far.

The people are at bay and gazing.

What else does Europe's culture seek.

My structure is awe ablazing.

Comment-allez vous

What building am I?