Please answer a question about the following article about Frédéric Chopin:

In June 1837 Chopin visited London incognito in the company of the piano manufacturer Camille Pleyel where he played at a musical soirée at the house of English piano maker James Broadwood. On his return to Paris, his association with Sand began in earnest, and by the end of June 1838 they had become lovers. Sand, who was six years older than the composer, and who had had a series of lovers, wrote at this time: "I must say I was confused and amazed at the effect this little creature had on me ... I have still not recovered from my astonishment, and if I were a proud person I should be feeling humiliated at having been carried away ..." The two spent a miserable winter on Majorca (8 November 1838 to 13 February 1839), where, together with Sand's two children, they had journeyed in the hope of improving the health of Chopin and that of Sand's 15-year-old son Maurice, and also to escape the threats of Sand's former lover Félicien Mallefille. After discovering that the couple were not married, the deeply traditional Catholic people of Majorca became inhospitable, making accommodation difficult to find. This compelled the group to take lodgings in a former Carthusian monastery in Valldemossa, which gave little shelter from the cold winter weather.

Where did Chopin and Sand stay in Valldemossa?
a former Carthusian monastery