EXCELSIOR SPRINGS – A block north of The Atlas Saloon, Grace Wins and The Farm House, a hill with a past and a future rises. “There used to be a hotel up there – Hotel Castle Rock,” Ryan Radecki says. The lawn at the hill’s base climbs up to a stone retaining wall, about 8 feet tall, at Main and Excelsior streets. The wall acts as a dam to hold back a hillside dotted by evergreens scattered among strangling brush. A few full-size trees yawn bare-limbed against a gray-blue sky. The Radecki family bought the wall, hill and history last month. With son Riley, 10, and wife Krissy, Ryan stands alongside the wall – ruins from the once wildly prosperous, quack-packed Ball Health Clinic – and later, a spa. “It became the Spa View Retirement Home,” Ryan says. “Around the ’60s or so, (the Ball clinic) was condemned and finished off, and so, what you see now are the remnants of those structures.” Before then, in 1905, Hotel Castle Rock opened in the city’s heyday when tourists drank their…