Łęczyca prospered in the period between the mid-14th and mid-17th centuries. The royal castle, built by Casimir the Great, was located on a small hill, protected by a moat with water from the Bzura river. The complex was made from red brick, set on stone foundations. It was protected by a 10-meter high wall, with a tower located in its southwestern corner. Gate tower was placed in the western wall, in the basement was a prison, and in the courtyard there was a two-storey tenement building. Rooms of that building frequently housed meetings of the Royal Council. In 1964, widespread renovation of the complex began. Another building was added at that time, which now houses the Museum of the Land of Łęczyca.