Ermita de Nuestra Señora de las Nieves is a small Catholic chapel beside Cañada Blanca Visitor Center and the Parador de Las Cañadas del Teide, more than 2,000 metres above sea level. It’s an easy add-on if you’re already stopping here, but I wouldn’t plan a separate visit around getting inside: regular public hours aren’t posted, and visitors often find the door locked. Treat the interior as a bonus.
The nearby Parador and visitor-center area is where to look for food and toilets; those are separate facilities, not chapel amenities. Parking is shared with the wider visitor area rather than dedicated to the chapel.