Opposite the Sheikh Lotfollah Mosque is the towering, six-storey Ali Qapu palace, a royal residence used by Shah Abbas to host visiting dignitaries. Completed at the end of the 16th century, it houses various paintings and frescoes, and the columned terrace boasts exceptional views of the square and its mosques. Depicted on the reverse side of 20,000 Rial banknotes, the palace is a national treasure, although much of the building fell into disrepair under subsequent ruling dynasties. The sixth-floor music room is a particular highlight for the wonderful shapes cut into the walls and ceiling.