bootstrap/docs/examples/tooltip-viewport/tooltip-viewport.css

body {
  height: 1200px;
}
.tooltip {
  min-width: 250px;
  max-width: 500px;
}
.tooltip .tooltip-inner {
  min-width: 250px;
  max-width: 500px;
  min-height: 200px;
}
.placeholder {
  height: 900px;
}
.container-viewport {
  position: absolute;
  top: 600px;
  left: 200px;
  width: 600px;
  height: 400px;
  background: #c00;
}
.btn-bottom {
  position: absolute;
  bottom: 0;
  left: 0;
}