[1] The lines, also known as Santa Margherita Enceinte, were built to the designs of the Dominican Cardinal Fra Vincenzo Maculano da Firenzuola.

The lines were designed by Vincenzo Maculano da Firenzuola, and were meant to protect the land fronts of Birgu and Senglea, and also to prevent a flanking attack on the capital Valletta.

[5][6] The lines were built on Santa Margherita Hill, known colloquially as il-Mandra,[6] possibly on the ruins of an ancient Greek temple or an earlier castle.

[5] The hill is featured in the account of the Great Siege of 1565 by arquebusier Francesco Balbi di Corregio, who mentioned that a belvedere existed on it.

At the time of completion in 1736, the Santa Margherita Lines consisted of five bastions, two demi-bastions, six curtain walls, three gateways, at least two sally ports, a ditch, a covertway with lunette, and a glacis.