Map download problem

OK, i can easily download addons and stuff and USE them in gmod like haxx ect. but when i download maps and drag them into the maps folder, when i open gmod they are not there. Whats going on? Im doing everything right (i think) and i cant play the maps that i just got (freespace). Help plox

Be sure to put the .bsp in the maps folder, not the whole folder.
Also, be sure to check the ‘Others’ category when starting a singleplayer game.

Thank you!