On their farm near Windsor, Illinois, Dave and Marcia Johnson built more than a goat tower: a Williamsburg-style house, a working replica of a King George VI palace gate, and an outdoor granite xylophone visitors can actually play. The tower itself is the centerpiece — 30 feet of brick with 276 steps spiraling up the outside to hollow “apartments,” built after Dave saw a photo of a similar structure at a South African winery and decided Illinois needed the third one ever made.