A video in the references.
According to the video, it is just a deck, or "cubierta" in Spanish.

Perhaps some synonyms may help:

monkey bridge - The Free Dictionary
www.thefreedictionary.com/monkey bridge‎
platform - a raised horizontal surface; "the speaker mounted the platform". ***2. monkey bridge - the highest navigational bridge on a ship; a small (often open) deck ...**
Noun 1. monkey bridge - a high narrow platform above a deck or in an engine room or boiler room
platform - a raised horizontal surface; "the speaker mounted the platform"
2. ****monkey bridge - the highest navigational bridge on a shipmonkey bridge - the highest navigational bridge on a ship; a small (often open) deck above the pilot house****
fly bridge, flybridge, flying bridge
bridge deck, bridge - an upper deck where a ship is steered and the captain stands

http://www.interglot.com/dictionary/en/en/translate/monkey b...
English Synonyms: more detail...
monkey bridge:
fly bridge ; monkey bridge ; flybridge ; flying bridge

http://translation.babylon.com/english/monkey bridge/
Noun
1. a high narrow platform above a deck or in an engine room or boiler room
(hypernym) platform
****2. the highest navigational bridge on a ship; a small (often open) deck above the pilot house
(synonym) flying bridge, flybridge, fly bridge*****
(hypernym) bridge, bridge deck

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Note added at 1 hr (2013-11-20 22:32:21 GMT)
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**** Amended answer*****
http://www.inglesmaritimo.com/docs/Soluciones.pdf
· Forecastle deck. Cubierta del castillo de proa
· Upper deck. Cubierta superior


http://www.btb.termiumplus.gc.ca/tpv2alpha/alpha-eng.html?la...
monkey deck Source 11, record 11, English, monkey deck
castillo de proa Source 11, record 11, Spanish, castillo de proa
MASC


So monkey deck "castillo de proa". HTH!

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Note added at 2 hrs (2013-11-20 23:45:35 GMT)
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Ines:

I am not shooting down your valid proposal. However, extensive research appears to indicate two different things: The term being requested is "monkey deck".

Further research:
http://en.wiktionary.org/wiki/Appendix:Glossary_of_nautical_...
crow's nest - Specifically a masthead constructed with sides and sometimes a roof to shelter the lookouts from the weather, generally by whaling vessels, this term has become a generic term for what is properly called masthead. See masthead.
masthead - A small platform partway up the mast, just above the height of the mast's main yard. A lookout is stationed here, and men who are working on the main yard will embark from here. See also Crow's Nest. I also posted a photo in my response to you.

http://www.navy.mil/navydata/traditions/html/navyterm.html
Crow's Nest
The raven, or crow, was an essential part of the Vikings' navigation equipment. These land-lubbing birds were carried on aboard to help the ship's navigator determine where the closest land lay when weather prevented sighting the shore. In cases of poor visibility, a crow was released and the navigator plotted a course corresponding to the bird's flight path because the crow invariably headed towards land.

The Norsemen carried the birds in a cage secured to the top of the mast. Later on, as ships grew and the lookout stood his watch in a tub located high on the main mast, the name "crow's nest" was given to this tub. While today's Navy still uses lookouts in addition to radars, etc., the crow's nest is a thing of the past.

fly bridge - definition of fly bridge by the Free Online Dictionary ...
www.thefreedictionary.com/fly bridge‎
Noun, 1. fly bridge - the highest navigational bridge on a ship; a small (often open) deck above the pilot house. flybridge, flying bridge, monkey bridge.

http://www.usmm.org/terms.html#anchor250442
Monkey island: A flying bridge on top of a pilothouse or chart house.