Spend a little time on a short interpretive trail near Lake Roosevelt. Views are nice, and there's lots of history to learn about.
From the parking lot, locate a large kiosk featuring some interesting information on Lake Roosevelt access. Look for the big brick building beyond the kiosk and head towards that. It houses a visitors' center and the bathrooms.
From the visitors' center, follow the lined path, taking your time to read the interpretive signs. The trail is all flat and the signage is interesting. The history is interesting, if from a depressing part of Washington's history. (It was an army fort, then a Bureau of Indian Affairs (BIA) boarding school, then a tuberculosis sanatorium). Most of the buildings are now gone, but a few remain.
Near the foundations of the Bachelor Officers' Quarters is a trail that leads to the beach, adding 0.8 miles to your outing. Another popular stop is the overlook on the Overlook trail, though it's not a great idea to visit if there is snow or ice present. The overlook trail is steep and narrow. In one place it is paved, but has an over 10% grade where it crosses a boulder field).