Attention Hogwart's students. This is Professor McGonagle speaking. In order for you to become witches and wizards, you must pass a series of tests, called Ordinary Wizarding Levels, or O.W.L.'s. The Hogwarts faculty members have created a test course that you must complete in order to receive your second O.W.L. This course, which is set in the middle of a muggle park, will test your abilities to hide your activities from muggles while practicing your wizarding skills. This course will test your mental and physical abilities. You will need to use your skills of observation, divination, and arithmancy.
This course consists of a number of hidden caches. Locating these caches is your primary goal. To find them, you must use a magical wizarding device, based on Gryffindor's Pointing Spells, or GPS for short. This will get you within about 10-15 metres of the caches, but you must use your divination and observational skills to locate them. Mysterious wordly and otherworldly forces can affect the accuracy of this device, so do not trust it entirely. If it leads you into poisonous plants or up or down steep terrains, you are looking in the wrong place.
Completing the first course, O.W.L.1 (GCQ7K7) is a prerequisite to starting the O.W.L.2 course. The final cache of that first sequence contains the location for the first cache in this sequence. Each cache in turn will point you to the next cache until you reach the final cache. You may also find some hints scattered about. Once you find the final cache, you will have passed the O.W.L. To prove that you found it, you must sign your name into a logbook in the cache. This cache has room for you to trade small magical items with other students, to commemorate your find.
O.W.L.2 is a long and hairy course, requiring plodding up steep hills on established trails. It requires a climb of over 140 metres and a distance of about 1.5 kilometres from the end of O.W.L.1. Only advanced students in good physical health should attempt the entire course. Some of the caches may be too high up for younger students to reach. Older students or adult wizards may help. A wizard's staff is highly recommended, for non-magical purposes.
You must follow muggle rules while you are here. All the caches are only a short distance from the trail. Beware of hazards, such as venomous plants, serpents, and giant spiders. Do not attempt this at night, as werewolves and lions are known to hunt here after dark. Remember to conceal your activities from muggles. Parts of this trail are exposed to the full rays of the sun. You may wish to bring a hat, but do not wear a witch's or wizard's hat.
Including the Hidden Secrets Trail and O.W.L.1, the total length of the 3 courses is 2.8 kilometres one-way with a maximum change in altitude of 158 metres. Plan your time accordingly should you choose to do them all at once.
Update 5/23/24: OWL1 final stage was muggled, requiring OWL2 to be disabled. OWL1's final had hints for OWL2. The hints are now in this listing.