From Madrid:

Take the N VI - road to La Coruña - up to Lugo. From Lugo take the N-640 up to Lalín, where you take the PO-200 until you can connect with the N-541 in direction to Pontevedra. Once you're in Pontevedra, you have to take the PO-12 up to Marín for 8 km. .