Avant-garde artist, linguist, esoteric philosopher, and close friend of Borges, Xul Solar is best known for his luminous, semi-abstract watercolors. They glow against the low-lighted concrete walls of this hushed museum. Solar's wacky but endearing beliefs in universalism led him to design a pan-language, pan-chess (a set is displayed here), and the Pan Klub, where these ideas were debated. One of its former members, architect Pablo Beitia, masterminded the transformation of the town house where Solar lived and worked. Open stairways crisscross the space, an homage to one of Solar's favorite motifs.