One of the entrances is in the great flanking facade to the Piazza Borghese that is extended by a slightly angled facade leading down Via Borghese towards the river.

Palazzo Borghese is the main seat of the Borghese family in Rome; it was nicknamed il Cembalo ("the harpsichord") due to its unusual trazezoidal groundplan. Its entrance facade faces the Fontanella di Borghese, with a great flanking facade in Piazza Borghese and a slightly angled extension down via Borghese to the river. Howard Hibbard demonstrated that the nine-bay section of palazzo was begun in 1560-1561 for Monsignor Tomasso del Giglio, whose arms remain over the door in Piazza Borghese, and he suggests that the architect was Vignola, an attribution accepted by Anthony Blunt and considered conclusive by James S. Ackerman followed by other scholars since, with more or less reduced interventions by Longhi.