Sant Mateu is a small medieval town in the interior of Castellón province in Valencia, Spain. It was once the capital of the Maestrat region and served as the seat of the Order of Montesa — the Valencian successor to the Knights Templar — which explains the grandeur of its Gothic archpriestal church and the scale of its arcaded Plaça Major relative to its modest size today.
The town is a worthwhile detour if you are travelling between Valencia and the Ebro Delta or Tarragona. The stone arcades of the main square are well preserved, and the Historical Museum has a good collection documenting the area's medieval history. Several Gothic palaces — among them the Palau Borrull — line the streets around the square, and the nearby Ermita dels Àngels makes for an easy walk out of town. It is a calm, unhurried place that sees relatively few tourists despite its architectural interest.