In San Bartolo Agua Caliente, a small rural town in the Mexican Volcanic Belt, a spa operates today amidst ruins of a much larger, ancient complex that originally included an orphanage, hospital, and a hostelry for travelers. This was one of the first colonial spas in Mexico. The spa was so well engineered that it remains virtually unchanged today from the time it was built at the very end of the 1700s. It uses the same outside and inside plumbing, and interior collection basins. The only change is the new pipeline that circumvents the original outside, hot water collection tanks that remain in good working order and are interesting to look at