Llyfrgell Genedlaethol Cymru / National Library of Wales

Perched on a hillside above Aberystwyth, this modernist building houses Wales's national collection of books, manuscripts and documents going back centuries. The architecture alone is worth the trip - all clean lines and brutal concrete, opened in 1937 and looking like it belongs in a different era entirely. You can wander the exhibition spaces free of charge, though the reading rooms require a reader's ticket if you want to actually dig into the archives.

Historians and serious book nerds will spend hours here. The collections are genuinely impressive - medieval Welsh manuscripts, first editions, maps, photographs. Less obvious for a family holiday, unless you've got teenagers interested in Welsh culture or your idea of a rainy afternoon involves browsing rare books. Most casual visitors pop in for thirty minutes to an hour, take in the building itself and maybe grab a coffee in the café.

The real draw is the context. You're staying at one of the nearby parks - Aberystwyth Holiday Village or Clarach Bay are both close - and this gives you something properly substantive to do on a slower day. Combine it with a walk around Aberystwyth town centre or a trip up Constitution Hill on the funicular railway. The library sits high enough that the views back towards Cardigan Bay are decent, even if you're not planning to spend half a day inside.

Free entry to the exhibitions. Allow 45 minutes to 2 hours depending on how deep you want to go. Weekday mornings tend to be quieter than weekends.