Mark 21 nuclear bomb
The Mark 21 nuclear bomb was a United States nuclear gravity bomb first produced in 1955. It was based on the TX-21 "Shrimp" prototype that had been detonated during the Castle Bravo test in March 1954. While most of the Operation Castle tests were intended to evaluate weapons intended for immediate stockpile, or which were already available for use as part of the Emergency Capability Program, Castle Bravo was intended to test a design which would drastically reduce the size and costs of the first generation of air-droppable atomic weapons (the Mk 14, Mk 17 & Mk 24). At long, in diameter, and weighing , the Mk-21 was half the length and one-third the weight of the Mk-17/24 weapons it replaced. Its minimum yield was specified at four megatons.
Castle of Castelo Branco
In 1981, structures that belonged to the GNR, and which were addorsed to the walls along the "Rua Vaz Preto" were demolished. During the course of the demolition of houses along "Rua Vaz Preto", part of the original wall and towers were re-discovered. This led to the 5 June 2009 proposal to seek a formal classification of the site's heritage status. On 26 October 2009, the DRCCentro requested the castle's classification as a "Property of Public Interest". It was accepted on 28 October by the consultative council of IGESPAR, but the process was archived on 7 January 2013, and the site never obtained its classification.