Very close to Castejon, There is pool formed in the river Dulce prior to entharbor in the town of Mandayona. In this section, the river has passed only three very small populations that are in the Natural Park of Rio Dulce, so its waters are clean and fresh. Just see it is a pleasure, and if you dare to bathe, I am sure you will want to repeat.
To get from Castejon, you have to take the road to Siguenza, and a little beyond km 6, towards Sigiienza, you will see a road and a house to the left of the road. Following the path, the pool is a little later, hidden behind a building in ruins and several Nogueras.