2F 3C is an awful tile in the economics/corp time period of the game. Better tiles:
-mines
-windmills
-riverside cottages of any kind, villages or better
-workshops
-watermills
-lumbermills
-environmentalism forest preserves
-riverside farms or any bio farm
-If you have the food resources, running a rep specialist owns the




out of working feitoria water tiles also.
Colossus is better and viable early game because 1) the opportunity cost is lower (there are fewer tiles that dominate the coast tiles) and 2) it's actually cheaper with copper than building multiple feitorias by a wide margin, and you get it in the highest hammer city (or close) rather than trying to work it into a junk filler.
So here we have a building that has its primary bonus as something that adds to the tiles you want to work least, and yet they remain the tiles you want to work least. To add insult to injury, you need a harbor first, but it would generally be an awful play to build the thing before granary and lighthouse at a minimum as well. All of this considered, and THEN you realize that for nearly half the game, you don't have it!
And you think that ISN'T a candidate for "worst UB"???
Technically, you can go as far as rifles + artillery using spain's UB. Definitely not to be underestimated.
Both obsoleted at calendar before BTS. In BTS, both don't obsolete until astronomy.