Given the following context:

During the first half of the 17th century, Swedish warships were built in the Dutch manner, with a flat, rectangular bottom with a small draft. This shipbuilding style was adapted mainly for smaller ships in the shallow coastal waters of the Netherlands, and allowed for quick construction, but these less sturdy vessels were generally unsuitable as warships and somewhat unstable in rough seas. When Kronan was built, the English approach to building had prevailed, giving hulls a more rounded bottom and greater draft, as well as a sturdier frame and increased stability. The stern was more streamlined below the waterline, which lessened resistance.The measurements for Kronan were recorded in contemporary navy lists. Its length from stem post to stern post was 53 m (174 ft); this was considerably shorter than the length if the bowsprit and beakhead were included. The width was 12.9 m (42 ft) and was defined as the widest point between the frames, excluding planking. The draft varied depending on how heavily she was laden, but with full stores, ammunition and armaments it would have been about 6.2–6.8 m (20–22 ft). The height of the ship from keel to the highest mast was never recorded, but Kalmar County Museum has estimated it to have been at least 66 m (217 ft).Kronan's displacement – the ship's weight calculated by how much water it displaced while floating – is not known precisely, since there are no exact records of the dimensions. By using contemporary documents describing the approximate measurements, it has been estimated at around 2,300 tonnes. By its displacement in relation to the number and weight of guns, Kronan was over-gunned, though this was not uncommon for the era. European shipwrights had not been building three-deckers on a large scale before the 1650s; by the 1660s, designs were still quite experimental. Contemporary records show that English and French three-deckers tended to be rather unstable because they were built high, narrow and with too much artillery. Some English ships had to be...

answer the following question:

What was estimated to be at least 217 feet? 

The height of the ship