Whichever of the museums you visit, one of the first things you’ll see will be the ancient steles (memorial stones, ‘hilarri’ in Basque) which are common throughout the Basque Country. And not just any old steles: the Basques specialised in very characteristic discoidal steles. (Despite ‘stele’ being a common archaeological term, it took us a while to get used to it, by which time we were habitually referring to these things as ‘discoidal what-nots’.)
The San Telmo Museum in San Sebastian, in the old San Telmo convent, recently redesigned with all mod cons, is highly recommended for its beautifully displayed survey of Basque archaeology, history and art: