Rivendell, also known as Imladris, is a city of elves founded by Elrond. At the time of Rivendell's founding, Middle Earth was in great turmoil. Sauron had grown powerful and seemed an imminent threat to the peaceful elven realms. Choosing a secure and difficult to find location for Rivendell was a strategic move by Elrond to protect his people. Rivendell is located in a "hidden valley" near the Misty Mountains on the edge of the Bruinen River.
Rivendell was also protected by elven magic which may have also helped shield it from unfriendly eyes. Elrond was a ring bearer, holding one of the three elven rings of power, Vilya, the mightiest of the three. Vilya had the power to protect and preserve and more than likely aided Elrond in preserving Rivendell. The Bruinen River defended the elven realm from the encroachment of the nazgul inLord of the Rings.