As he’s gazing out from the front porch what surprises Percy about the summer camp?

From the text:

We must’ve been on the north shore of Long Island, because on this side of the house, the valley marched all the way up to the water, which glittered about a mile in the distance. Between here and there, I simply couldn’t process everything I was seeing. The landscape was dotted with buildings that looked like ancient Greek architecture-an open-air pavilion, an amphitheater, a circular arenaexcept that they all looked brand new, their white marble columns sparkling in the sun. In a nearby sandpit, a dozen high school-age kids and satyrs played volleyball. Canoes glided across a small lake. Kids in bright orange T-shirts like Grover’s were chasing each other around a cluster of cabins nestled in the woods. Some shot targets at an archery range. Others rode horses down a wooded trail, and, unless I was hallucinating, some of their horses had wings.