Wondering what this thing might be, I looked in the OED.
It says that a pergola is foreign (Italian), "any arbor, boure or close walke of boughes, namely of vines" and goes on to define thiss this as
1. "an arbour formed of growing plants trained over trellis-work, especially on a covered walk so formed." The 1st example is "a shed so contrived with a Cover, so as to exclude or admit the Rain, snow and weather at pleasure." Why one would want to do this, I don't know, so
still confused, I went to
2. "An elevated stand or balcony." Someone built it "to view the sports." This makes more sense, but I wondered what sports, especially since they have said it is covered and hidden with growing plants.

I can think of sports best kept hidden, but I wouldn't want to accuse you of such things, especially without the testimony of reliable witnesses such as Catspaw and Gargoyle.