Des O’Sullivan gets closer to nature on the spectacular treetop walkway.

More than a foot of rain has washed out highways around the US capital, toppled a 100-year-old elm tree on the White House lawn and caused flooding that closed major government departments and the National Archives, where the Declaration of Independence is kept.

MUCH of the US capital was forced to shut down yesterday after a weekend of heavy rain left washed-out roads and mudslides, blocking key routes in and out of Washington DC and causing widespread damage.