The first archaeological findings around the lake belong to nomadic people living in the area in prehistoric types. The first settlements discovered date from the Copper Age. The area was later under the control of the Ligures, later replaced by the Celts. The latter were in turn conquered by the Romans, who called the lake Verbanus Lacus or Lacus Maximus. After the fall of the Western Roman Empire, the lake was under different dominations. Most of the current settlements originated in the Middle Ages, when the lake was under the Della Torre, Visconti, the Borromeo and Habsburg families. Methane was first discovered and isolated by Alessandro Volta as he analysed marsh gas from Lake Maggiore, between 1776 and 1778. In 1936, a Bugatti Type 22 Brescia Roadster, built 1925, was sunk in the lake by employees of Zürich architect Marco Schmucklerski, when Swiss custom officials investigated whether he had paid taxes on the car. The Bugatti was attached to an iron chain making it possible to recover it once the investigation was over, yet that never happened. When the chain corroded, the car sunk to the lake bed, where it was rediscovered on 18 August 1967 by local diver Ugo Pillon and became a favourite target for divers thereafter. When one of the divers, Damiano Tamagni, was killed in a hold-up on 1 February 2008, his friends from the Ascona divers' club decided to lift and sell the carwreck to raise funds for a yet to be created foundation named after the victim. The remains of the Bugatti were recovered on 12 July 2009. The sale took place at the Retro Mobile classic car exhibition in Paris on 23 January 2010. It was sold for €260,500.
Question: How many families controlled the lake in the Middle Ages?
Answer: 4