There are three sets of caves open to the public in the natural park (and a fourth, Moeda, off the N356 road between Batalha and Fátima), but unless you are a real fan, a visit to one will probably suffice. As it happens, the largest and most spectacular, at Mira de Aira, is the only one directly accessible by bus.
Grutas de Mira de Aire
It’s a fabulous thirteen-kilometre drive out into the hills along the N243 from Porto de Mós to the Grutas de Mira de Aire, Portugal’s largest show caves. There’s parking right outside, or it’s a signposted one-kilometre walk from the town bus stop. The 45-minute guided tour ends up at a natural lake filled with fountains 110m below the surface, taking in a galaxy of stalactites, stalagmites and oddly shaped rock formations with curious names – “Octopus Gallery”, the “Organ”, the “Conch” – en route. To exit, you take the lift up and emerge beside the Parque Aquático water park (summer only), which is a great place to cool off – there are half-day and full-day tickets available for this, and you can visit independently of the caves. Outside on the road, several cafés and restaurants cater for the crowds.