1Trinity College Library – Dublin

The number one must-see on a trip to Dublin isn’t the Guinness Storehouse, it’s Trinity College’s Old Library. Construction on the Long Room, the library’s iconic main hall, began in 1712 and lasted 20 years.

The original structure only had books on the lower level, but when the library’s shelves were filled in the 1850s, the ceiling was raised to accommodate even more books.