How about this interiors? They are big and awesome to become duel arenas.
Interior 1
AddPlayerClass(230,2217.0928,1553.7535,1004.7188,358.1661,0,0,0,0,0,0); //
AddPlayerClass(230,2173.5452,1619.7195,999.9810,269.1592,0,0,0,0,0,0); //
Interior 14
AddPlayerClass(230,-1361.0297,1599.4950,1052.5313,90.7110,0,0,0,0,0,0); //
AddPlayerClass(230,-1491.2402,1595.5072,1052.5313,269.6360,0,0,0,0,0,0); //
Interior 15
AddPlayerClass(299,-1331.7242,991.0515,1025.0311,90.9308,0,0,0,0,0,0); //
AddPlayerClass(299,-1462.7218,997.1155,1025.1580,268.7858,0,0,0,0,0,0); //
I checked the ID of this interior and it's still the same as Interior 1 but this place that I'm about to refer is called warehouse.txd.
AddPlayerClass(230,1359.9630,-45.9597,1000.9254,309.8368,0,0,0,0,0,0); //
AddPlayerClass(230,1413.8563,2.7996,1000.9247,131.8500,0,0,0,0,0,0); //
P.S Please ignore the 1st number.