You get the answer by looking at the core of your sentence, removing all the qualifiers and subordinate clauses:
The Center is a building.
Notice that this would not work at all without the article a.
Now as we add the supporting information back in, we see that we need to keep the article a at each stage:
The Rio Sul Center is a building.
Opened in 1982, the Rio Sul Center is a building.
Opened in 1982, the Rio Sul Center is a 164-meters high building.
However, with that all said, your structuring of this sentence is still somewhat awkward, and difficult for a reader to parse, which is perhaps the root of your teacher's issue. I might suggest one of the following alternatives.
Opened in 1982, the Rio Sul Center is a building that is 164 meters high.
The Rio Sul Center opened in 1982 and is 164 meters high.