The Long Room, Trinity College
This is the main chamber of the Old Library at Trinity in Dublin, built in the first half of the 18th century. It houses 200,000 of the college's oldest books. On the ground floor below is a wonderful exhibit on the Book of Kells, leading to the Treasury where two facing pages of the Book itself are open to view. Dating from the early 9th century, it is renown for "its lavish decoration, the extent and artistry of which is incomparable". The large-scale displays on exhibit are truly impressive, accompanied by extensive explanatory texts. It was a fascinating visit.
The extra displays a lovely side staircase at the entrance to Long Room (an ultra-dark image rescued by much lightening in Photoshop :) It's stunning against the dark background.