This postcard from Russia is a perfect depiction of what I imagine Moscow to look like. Trading postcards through Postcrossing has been a phenomenal experience. You can get them as often as you like and are willing to send them, as you have to send one to receive one.
At the first level you sign up to send cards to whatever addresses are assigned to your account. You also receive cards from random countries each time one of your sent cards gets registered.
But on the next level you can sing up for the Forums on Postcrossing and choose to do tags, trades, notebooks, round robins, pen pals, postcards art, fan clubs and more. If you don't see one you were looking for, you can always start your own swap. If this is new to you then you should spend some time reading through what other people are doing here so you can understand what the expectations are, the lingo and how things work.