Inside this cockeyed dome in St. Petersburg, Fla. - the dome is not your typical dome, it slants to one side, built that way so they could air condition it easier and for cheaper - and there are four rings from the top of the dome all the way down to just above the bleachers.

Last night Tampa's Carlos Pena skied a fly ball to center field with the bases loaded in the sixth inning, and the ball hit the B ring catwalk, ruled in play wherever it lands. The ball dropped into shallow center field, all three runners scored and Pena was on second with a dome-aided double.

The rules on the catwalks are this - if the ball hits the B ring, as it did last night, the ball is ruled in play. If it comes down and someone catches it, it's an out. If it hits the C ring or the D ring - the two lower level catwalks - the ball is ruled a home run.

Why, you ask? The C and D ring are far enough away that if the catwalk didn't impede with the flight of the ball, it would easily reach the seats. A few years ago, I believe Troy Glaus accomplished this feat.

This differs from the rules in Minnesota's Metrodome, where the Angels play this weekend. While there are no catwalks in the place affectionately named the Homer Dome, there are speakers that hang in the middle of the place. If a batted ball hits one of those speakers - Mo Vaughn did it once - it is a ground-rule double.

Players might be upset about the odd rules of a dome and the little intricacies that come with it, but they will usually say the same thing - "That's baseball." And, I guess that's why each stadium is so unique, adding that extra level of fun or oddity to each game.

No way in football or basketball can something so odd affect a game. Think of the Green Monster in Fenway, or the hill in center field at Houston, maybe even the short right field porch in Yankee Stadium, the ability to hit a home run into the water in San Francisco or perhaps even the chance that a ball gets lost in the ivy-covered walls in Wrigley Field.

It is the only sport where the playing field is determined by each stadium, not some blanket rules governing the entire sport.