Woe betide the parent who actually tries to do that, at least in Washington, D.C. Per The Washington Post, on Capitol Hill—the epicenter of the nation's capital—a couple recently built an 8-foot-high treehouse for their young daughters, ages 3 and 5. Ellen Psychas counsels high school students. Bing Yee is a lawyer for the Department of Homeland Security. They checked with the city and found no regs prohibiting them from building a treehouse on the U-shaped alley behind their house. The couple says they passed out fliers alerting neighbors of their plans to build it. They paid an arborist $300 so they could avoid harming the 100-year-old elm in which the treehouse was being built. Soon, the 30-square-foot castle-themed treehouse was up.