The opposite is outdoors.
The opposite of "indoor" is "outdoor".
Indoor sports are just indoor sports. But if you want to get specific then you might say indoor soccer, indoor tennis, indoor football, etc.
An indoor riding arena is an indoor area where you can ride horses.
The word 'indoor' is generally used as an adjective, as in 'indoor activities', indoor swimming pool', etc.
Indoor soccer
In college you can play: Indoor Soccer Indoor Handball Indoor Swimming Indoor Floor Hockey Ice Hockey Basketball Football Baseball Golf Indoor Tennis Indoor Volleyball Dodgeball (Intramural) Dance Team Cross-Country
an indoor stadium
National Indoor Arena is an indoor arena in United Kingdom and was opened on 1991.
You can get information on indoor gardening at Indoor-gardening-guide.com. You can also visit Gardenhobbies.com.
You could, but outdoor arenas are often called menages, an indoor arena can be called a indoor school, or an indoor arena.
Name s of the indoor games
Indoor temperature is the temperature indoors.
indoor