At the Uyuni salt flats in Bolivia we stayed in a hotel made from salt blocks. The roof was not salt, the floors were crushed salt (not recommended for bare feet!), and the bathrooms were tiled. This hallway view shows the construction and gives a small glimpse into my room. The gray stripes in the salt blocks are accumulations of ash from eruptions of Andean volcanoes nearby. Chemistry dictates that the mortar must include salt.