Complex sentence: The building is located at 725 17th Street NW, on the north side of Pennsylvania Avenue across from the Old Executive Office Building (Eisenhower Executive Office Building), which is next to the White House.
Split into simpler sentences: The building is located at 725 17th Street NW, on the north side of Pennsylvania Avenue. To the south are is the Old Executive Office Building (Eisenhower Executive Office Building), which is next to the White House.