The ground. Sometimes it's made to sound like a plane in another dimension. "It's not the place to be in a real fight, Other people will kick you, No good against multiples, It's harder to get away."
It's just the ground for God sakes. It's been there, in contact with us, almost every minute of our lives. The place not to be in a real fight is on an escalator, or the edge of a building, or in car. The ground is just fine.
We used to train the ground in a lot of ways. Being surrounded by people who were going to kick or stomp (big difference) or jump on. You have to train using your arms to turn yourself (your feet) towards all directions, you have to use and train various umbrella' tehniques to shield your head. You have to practice quick, violent rolls towards surrounding legs. And you have to do that carefully to avoid injuries while training - you'll hyper-extend their knees and hyperextend/crush ankles if you go wild.
There's some great ways to train on the ground - or more appropriately, fight on the ground while getting up. And let's be honest here - how many of you actually practice getting up as fast as humanly possible? I'm talking the ground has just caught fire getting up. And how often do you do it? Because you should.
In any dojo I ever taught - getting up from any exercise, or two man set, or while sparring (after setting defensive/offensive guard - then deciding to get up) or stretching (other than really long splits) is done as if the ground just caught fire. I can't actually envision any other way off getting up off the ground in a dojo. Same way you get up in a fight, when you do get up, really f'n fast. I think you're nuts if you don't practice that.