More than 20m wide and 230m deep, the Gouffre de Friouato is said to be the deepest cavern in North Africa, and the cave system is possibly the most extensive. It was first investigated in 1935, and access leads down 520 precipitous steps (with handrails) to the floor of the cavern.
A return grand taxi from Taza Haute costs Dh300 and up, depending on how much time you want to spend here.
Once you reach the bottom of the stairs, you can squeeze through a hole to start exploring the fascinating chambers that are found 200 more steps below. It’s dark and eerily beautiful: wear clothes you don't mind dirtying, but be prepared for a strenuous climb back up.
The most spectacular chambers, full of extraordinary formations, are the Salle de Lixus and the Salle de Draperies. They do indeed resemble thin sheets of curtains, frozen and calcified. Allow at least three hours there and back. Speleologists have explored to a depth of 300m, and they believe there are more rooms another 500m below.
The admission fee allows you to enter the cavern mouth at a depth of 160m. Beyond that, a guide (hire at the entrance) is needed to go further underground to the grandest chambers. Bank on the occasional scramble, and be prepared to squeeze through narrow sections; it's not recommended for claustrophobes. Overalls, nonslip overshoes and a helmet with lamp must be rented. Take the protective gear seriously – people have been killed here by falling rocks.
Gouffre de Friouato is well signposted, up a very steep road 25km from Taza. There's a small cafe close to the entrance.