Starting May 1, visitors to Big Bend National Park won’t be able to access the Chisos Basin—including the campground there and some of the park’s most popular trails. But while crews are busy demolishing and rebuilding the main lodge and putting in new water lines, the rest of the park will remain open during a major revamp that’s expected to last about two years. That means now’s a good time to explore some of the park’s lesser-known areas.The construction project includes a new main building that will house hotel check-in, a restaurant, and gift shop. (Existing guest rooms will not be torn down or renovated, but they will get spruced up.) During the demolition period early on, when heavy trucks will need to reach the…