1) The concept of virtual reality (VR) involves creating a simulated environment that can be explored and interacted with using specialized headsets and input devices.

2) The discovery of the Americas by Christopher Columbus in 1492 opened up new trade routes and had a profound impact on world history.

3) The Berlin Conference in 1884-1885 divided Africa among European powers and set the stage for the colonization of the continent.

4) The world's largest particle accelerator, the Large Hadron Collider, is located near Geneva, Switzerland, and spans a circumference of 17 miles (27 kilometers).