Nidaros Cathedral is Scandinavia's largest medieval building. Outside, the ornately embellished, altar-like west wall has top-to-bottom statues of biblical characters and Norwegian bishops and kings, sculpted in the early 20th century. Several are copies of medieval originals, housed nowadays in the museum. Within, the cathedral is subtly lit (just see how the vibrantly coloured, modern stained-glass glows, especially in the rose window at the west end), so let your eyes attune to the gloom.
The altar sits over the original grave of St Olav, the Viking king who replaced the Nordic pagan religion with Christianity. The original stone cathedral was built in 1153, when Norway became a separate archbishopric. The current transept and chapter house were constructed between 1130 and 1180 and reveal Anglo-Norman influences (many of the craftsmen were brought in from England), while the Gothic choir and ambulatory were completed in the early 14th century. The nave, repeatedly ravaged by fire across the centuries, is mostly a faithful 19th-century reconstruction.
Down in the crypt is a display of medieval carved tombstones (the majority restored from fragments since many headstones were broken up and carted away to be recycled in domestic buildings). Look for one inscribed in English and dedicated to William Miller, Shipmaster, of Dundee, Scotland, who met his end near Trondheim in the 18th century.
You can wander around freely but, between early June and early August, it's worth joining a tour (a 15-minute canter or a more detailed 45-minute visit). Times vary but there are up to four daily in English. Music-lovers may want to time their visit to take in a recital on the church's magnificent (and recently restored) organ.
From early June to early August, you can climb the cathedral's tower for a great view over the city. There are ascents every half hour from its base in the south transept.