I can't go 20 miles in any direction without 2,000 feet of elevation gain, and our terrain is just ordinary rollers, no real mountains.
Can't even do a textbook FTP test here. The only way to ride 20 minutes on flat terrain is to find a big parking lot and go in circles. Pretty much what the local crits do.
For that matter, riding a crit might be the best way to do an FTP test here anyway. I'd need to ride pretty close to maxed out just to keep up with those women. Forget the guys, I'd be dropped the first lap.
The only somewhat flattish terrain I can think of is mostly sluggish pavement -- chipseal, striated concrete, etc. -- the stuff that feels like riding in hard sand. Even then there's no continuous riding for more than a couple of minutes between intersections.
On the plus side, solo riding mostly rural roller coaster routes has made my occasional dabbling in semi-fast group rides a little easier.