Sé de Lisboa (Cathedral) is a real time commitment — fit it in only if it's a priority.
Allow 30–45 min.
A stout, twin-towered Romanesque pile that has survived since the 12th century and several earthquakes — atmospheric and free to enter the nave. The catch: the interior is austere and dim, the cloister and treasury cost extra for fairly modest returns, and it photographs better outside (with a tram passing) than it rewards inside. A quick, free, worthwhile pause.