The Rapidan is the top-rated stream in the park. It deserves it, but gets tons of pressure. Anything that stays wet all year round will have brookies in the park. Get Harry Murray's book, it lists all the good streams in the park. The productivity of each stream changes year-to-year, so it's tough to say exactly where to go. The charm of the SNP is hiking a few miles to a hole that nobody knows exists, and pulling beautiful wild native brook trout out of it.