Arcadia, Oklahoma:
Round Barn, Giant Soda Bottle, 2nd Largest Cross on 66

Arcadia offers one Route 66 landmark that dates back nearly 30 years before the Mother Road was routed, and another attraction that's nearly brand-new.  If you're headed westbound, as I was (and as the song says you should be), you'll first come upon Arcadia's old treasure: the appropriately named Round Barn.  The round, red structure sits on a small hill, right beside the Route. 

I arrived too early to get inside--the barn was locked tight.  A little later in the day, and I could have checked out the gift shop inside.  Even though the inside wasn't open, I was still free to walk around the outside, allowing me the authority to verify that, indeed, this barn is indeed round. 

... that stands in front of Pops, a combination gas station/restaurant/convenience store/tourist trap.  In keeping with the soda theme, the store has an entire wall lined with refrigerated cases, each one holding dozens of varieties of soda pop.  You'll find local "brews", brands you never knew existed, flavors you haven't tasted since you were a kid, and of course, Coke and Pepsi.  The front windows are also lined with thousands of bottles of soda, just to look cool.

Sure, the sodas are expensive ($1.99 a bottle) and so are the gifts, but it really doesn't matter.  This place is just pure fun.  It's also a bit surprising that such a place is miles away from the nearest Interstate (I-35 is 4 miles away).  I think it's a true testament to Route 66's ability to still bring in travelers for local businesses.

And get this: the soda bottle is 66 feet tall.  Coincidence?  Pops says that's big enough to make it the world's largest soda bottle.

Those rings are illuminated with color-changing LED lights at night, creating what must be one of the greatest signs on the Mother Road.

Once you leave Pops, you'll probably be hoping to see more things that are larger than life, and a religious display in nearby Edmond, Oklahoma won't disappoint.  As OK 66 crosses over I-35, keep an eye out for this giant cross next to a mega-church.  Don't be too impressed, though: it's not the biggest cross you'll see on this Route 66 road trip.