Way down south, where the Rio Grande meets the Devil’s River, lies Lake Amistad. A pellucid lake, with waters transparent enough for scuba divers, it is edged by sheer cliffs and a picturesque shoreline. Float in a houseboat and anchor where you please for barbecues and beach volleyball. By kayak, however, you can move into the lake’s more narrow recesses. There, seek out the various archeological sites, such as the 4,000-year-old pictograph sites in Panther and Parida Caves, located on the upper portions of the lake.