The round is the top part of the back legs, and is a big piece of meat. They are almost always disappointed by a degree of toughness that is truly hard to imagine for such a pretty cut. The top round is, however, the best cut for making poor boys. She said to sear it, then put in into just enough water that the beef almost floats. Then simmer it for hours and hours with the usual savory vegetables.
Top round is also a good steak cut.
It's the classic cut to use when making Cuban steaks or carne asada. A Cuban steak is about a half-inch thick and cut across the round to produce a steak big enough to hang off all but the biggest plates. It's seasoned with garlic and onions and mojo criollo, and it's terrific. You can marinate the round for Cuban steak if you like, but unless the grade is really terrible that's not really necessary. One aspect of round that you should consider is that it has what I find to be the mildest flavor of all the possible steak cuts.