Does "坊" also mean "square", "plaza", "piazza" like "广场"?
The 坊 in 金马碧鸡坊 refers to 牌坊. There is a 金马牌坊 and a 碧鸡牌坊 as mentioned in the Wikipedia article.

In the olden days, an arch known as 牌坊 is used to mark the entrance to a city subdivision. From Wikipedia:


  The largest division within a city in ancient China was a fang (坊),
  equivalent to current day precinct. Each fang was enclosed by walls or
  fences, and the gates of these enclosure were shut and guarded every
  night. Each fang was further divided into several pai (牌; literally
  "placard"), which is equivalent to current day (unincorporated)
  community. Each pai in turn, contained an area including several
  hutongs (alleyways).


The most busy part of a town is usually at the gateway where the thoroughfare is. In modern times, 牌坊 only serves as a monumental structure.

The word 坊 has several other meanings. Including:

街市 (street market) and
里巷 (lane, e.g. 兰桂坊)


Nowadays, the usage has been extended to represent a place filled with activities, including a square, a plaza or even a shopping mall e.g. 朗豪坊.