Forget the heavily edited Instagram reels. The reality of hiking to Rio Celeste involves sweat, a distinct smell of sulfur, and—depending on the season—ankle-deep mud that will claim your favorite white sneakers. But the payoff is entirely worth it. That surreal, neon-blue water isn’t a camera trick. It’s a bizarre chemical reaction, and seeing it cut through the dense green of Tenorio Volcano National Park is one of the best things you can do in northern Costa Rica. I’ve done this trek. Here is exactly what you need to know to get in, see the river at its bluest, and get out without ruining your rental car or your afternoon.…