Charles Rennie Mackintosh's greatest building – extensively damaged by fire in 2014, and due to re-open in 2018 – still fulfils its original function, so just follow the steady stream of eclectically dressed students up the hill to find it. It's one of Glasgow's architectural showpieces and has now been joined by Steven Holl's spectacular glacial, green School of Design right opposite. A risqué combination, but it works. Tours leave from the new building, which also holds a free design exhibition.
Visits to the Mackintosh building are by excellent hour-long guided tours (11am and 3pm, plus 1pm May to September, multilingual translations available) run by architecture students. While reconstruction is ongoing, they visit the building's exterior only. Book online or by phone at busy times. Once the building is reopened, tour frequency will likely increase.
Particularly impressive is the thoroughness of the design; the architect's pencil seems to have shaped everything down to the smallest detail. The interior is strikingly austere, with simple colour combinations (often just black and cream) and the uncomfortable-looking high-backed chairs for which Mackintosh is famous. The library, designed as an addition in 1907, is a masterpiece.
There's a Mackintosh shop at the end of the tour. If you liked the visit, the same folk run recommended architecturally minded walking tours of central Glasgow; see the website for details.