Montelbaans Tower. Rembrandt loved to sketch this slightly leaning tower, which dates from 1516; in those more perpendicular days, it formed part of the city's defenses against raiding hoards of Gelderlanders. City expansion in 1578 saw it connected by a defensive wall with the Sint Antoniepoort (De Waag in Nieuwenmarkt). It is traditionally thought to be the spot where the first Jewish refugees from the Inquisition in Spain and Portugal arrived. It was certainly the ferrying point to the sailing ships anchored in the IJ that were set to depart to the East Indies. In 1606, the ubiquitous Hendrick de Keyser oversaw the building of a new tower complete with clockworks. But time soon saw the tower leaning toward Pisa, and in 1611 it had to be reset with lots of manpower and ropes on a stronger foundation. Since 1878, it has housed the City Water Office, which maintains the water levels in the canals and engineers the nightly flushing of the entire city waterway system, closing and opening the sluices to change the direction of the flow and cleanse the waters (algae and the use of yacht toilets on houseboats make it a thankless job).