A medieval chapel dedicated to Our Lady of Pena stood high in the Sintra Mountains before King Manuel I founded a Hieronymite monastery there in the early sixteenth century. A small religious community occupied cloister, chapel, cells, and service spaces in an exposed landscape. The Lisbon earthquake of 1755 damaged the monastery, and religious orders were dissolved in Portugal in 1834. The abandoned complex and surrounding heights attracted Ferdinand of Saxe-Coburg and Gotha, husband of Queen Maria II, whose Romantic interests joined architecture, collecting, gardens, and dramatic scenery.

Ferdinand acquired the ruins and nearby land and commissioned the German-born engineer and architect Wilhelm Ludwig von Eschwege to create a royal retreat beginning in the 1840s. Rather than erase the monastery entirely, the project incorporated its cloister, chapel, and portions of residential fabric within a new palace. Towers, domes, battlements, gateways, terraces, tiles, sculpture, and painted façades freely combined Manueline, Moorish, Gothic, Renaissance, and other references. The design was deliberately eclectic and theatrical: a genuine nineteenth-century Romantic composition, not a scholarly reconstruction of a medieval castle.

Ferdinand shaped the surrounding park with winding paths, viewpoints, lakes, exotic and native plants, and collections gathered from many climates. After Maria II's death he continued using Pena and later shared it with his second wife, Elise Hensler, Countess of Edla. The Portuguese royal family made the palace a summer residence. King Carlos I and Queen Amélia occupied it before the monarchy fell in 1910; the palace then passed to the state. Its interiors retain room arrangements, decorative finishes, furniture, and objects associated chiefly with nineteenth- and early twentieth-century royal life.

Public museum use and intense exposure to wind, rain, fog, vegetation, and visitor traffic require ongoing conservation. Roofs, render, vivid exterior colors, tile, stone, timber, decorative painting, textiles, and park plantings have been repaired or renewed in documented campaigns. The palace contains authentic former-monastery fabric and substantial original Romantic construction, but later restoration and replacement are unavoidable. Modern pathways, barriers, transport systems, climate control, fire protection, cafés, and visitor services support access. Photographs from different periods may show color schemes altered before research-based restoration.

Parques de Sintra–Monte da Lua manages Pena Palace and Park as a heavily visited, timed and ticketed monument within the Cultural Landscape of Sintra World Heritage Site. Access, shuttle arrangements, interior routes, and closures follow current capacity and conservation rules. Pena should not be judged by the age its medieval-looking forms pretend to possess; their artifice is central to the Romantic project. Its history joins a surviving monastery, royal patronage, global botanical collecting, constitutional monarchy, republican nationalization, tourism, and continuous restoration of a purpose-built fantasy whose authentic nineteenth-century fabric was designed to look many centuries old.