Before the day is over, it’s very worthwhile to double back a few miles to Àger and see another one of nature’s great spectacles: a starry night. The mountains of the Montsec, an official Tourist Destination and Starlight Reserve, are home to the Centre d’Observació de l’Univers, where young and old alike learn a little bit more about the mysteries of the cosmos. After an intense, exciting day we set off for La Pobla de Segur, the end point of the historic Tren dels Llacs a journey offering spectacular panoramic views.