Khar Balgas is an ancient fortified city dating back to 744 AD and was populated until 840, depending on which sources you read. There is a small museum at the site which will be opened by a caretake if you show up. The cache is a plastic cliplock container with a green lid. It contains a pencil, logbook and at the time of placement a Mongolian fridge magnet. It is, as is typical, placed in a nook with the entrance covered by stones. While we have not tried to make this difficult to find, there are about 50 million stones stacked in this location. An amazing site.