At the same time government officials will be trying to show that Rocky Flats National Wildlife Refuge is clean and safe for visitors, a judge will be hearing testimony about why the former nuclear weapons manufacturing site should forever remain closed to the public. That juxtaposition over the future of the 6,200-acre property 16 miles northwest of Denver, which comes to a head this week, aptly illustrates the complicated legacy of what was one of the nation’s most contaminated Cold War sites that is currently trying to reinvent itself as a rare urban oasis for those wanting to experience the prairie’s unique ecology and wildlife. On Tuesday, a federal judge will hear evidence from a lawsuit filed by Rocky Flats opponents, who are asking him to block construction of trails and a visitor center at the refuge.