While the beggar held on to Peter and John, all the people were astonished and came running to them in the place called Solomon's Colonnade.So far, all we know is that (1) it is a place near the temple, (2) the disciples met there, and (3) it rhymes with "lemonade".
Acts 3:11
The apostles performed many miraculous signs and wonders among the people. And all the believers used to meet together in Solomon's Colonnade.
Acts 5:12
But what is a colonnade? BibleGateway.Com notes that it "was an open, roofed 45-foot walkway with double columns that were 38 feet tall. It was situated along the east side of the Court of Gentiles (Westerholm 1988:772). Although it was part of the temple complex, it was not considered to be part of the actual temple (Brown 1966:402), as evidenced by the fact that Gentiles were not allowed into the temple but they could be present in Solomon's Colonnade." And Bible-History.org has up a little picture of what it may have looked like.
So basically, Solomon's colonnade was a small porch by the temple, surrounded by columns. A perfect place to worship God with both Jews and God-fearing Greeks, while staying out of the rain!