Staging the operatic behemoth that is Berlioz's Les Troyens comes with huge challenges to harness the artistic, technical and dramatic qualities in a work which spans more than four hours. Staggering in scale and numbers, San Francisco Opera's current production of Les Troyens, the third staging since its 2012 première at London's Royal Opera House followed by Milan's Teatro all Scala in 2014, is a mighty spectacle supporting 134 artists on stage and 95 musicians of the San Francisco Opera Orchestra. Here, the vast resources have been turned into something memorable but mixed results in overall dramatic thrust left it often feeling hollow.

From the pit, former music director of the San Francisco Opera, Donald Runnicles returned to lend Berlioz's sweeping score a nuanced, handsome and unhurried eloquence. For its duration Runnicles gave attentive support to the large cast of soloists, never overwhelming the mostly exceptional individual performances.

In the opera's distinct two-part form, soprano Michaela Martens commanded the stage as the Trojan prophetess Cassandra in the two acts depicting The Fall of Troy. Martens' performance carried a magnetism which enthralled as she projected with voluminous ease her character's convictions with deep dark colours and a harrowing vibrato.

After sacrificing herself in death in order to protect herself from being raped by the invading Greeks, Martens' performance continued to resonate but was equally manifested in the multi-faceted richness which Susan Graham embodied as the compassionate Carthaginian ruler Dido as the epic's second part traverses Acts III–V. Broad, open top notes and effortless control throughout her range accompanied a clarity of music and diction of aesthetic harmony. Graham worked impeccably in duets to raise immediate drama beyond event with the steady, robust tenor of Bryan Hymel's Aenaes and the warmth and glow of Sasha Cooke's mezzo-soprano as Dido's sister, Anna. 

As Coroebus, a young prince from Asia betrothed to Cassandra, Brian Mulligan's attractive sauntering, smooth and smoky baritone flickered alongside Martens' Cassandra, giving his character an uncertain strength in his own outward confidence.

René Barber impressed as Iopas with a fertile-rich quality to his tenor and Christian Van Horn as Narbal, minister to Dido, was outstanding in bass strength and variegation. Philip Skinner as King Priam and Buffy Baggott as Queen Hecuba added vocal glitter as they soared gloriously over the chorus. Sadly the chorus failed to transform Berlioz's own French libretto into meaning which got lost in a clouded, unshapely largesse. Only when the genders split did fullness of sound coalesce with striking beauty.

In a letter to the critic Fiorentino, Berlioz referred to his five-act grand opera as his machine. If Berlioz's description provided any hint for director David McVicar and set designer Es Devlin, it came in the form of the majestic, stage-dominating and fearsome Trojan horse – a conglomeration of munition leftovers which moved with mechanical might, providing a pivot for a mid-19th century Crimean War-inspired setting of Virgil's epic poem, The Aeneid. Complemented by a four-level drum of seemingly impenetrable industrial strength for Troy's setting, then rotating to reveal a sun-drenched moorish colosseum-like structure which embraced a disc-shaped model of the city of Carthage in Acts III–V, the creative elements impressed immeasurably.

Disappointingly, however, these elements weighed heavily on a storytelling which suffered loss of detailed focus with perhaps something lost in revival director Leah Hausman's responsibilities. Thankfully the only apparent bait that dangled an association with what transpires as an irrelevant Crimean War concept seemed to be in some of Moritz Junge's military costumes. Any more and it would have confused the story's context.

Throughout the four hours of stage time, the enormity of scale was unceasing, rarely lending a hand to dramatic intimacy. Martens certainly had the presence to portray Cassandra's urgent, frenzied prophesy of doom, but it felt lost in a vast industrial emptiness. When Dido sinks into delirious rage after Aenaes succumbs to the gods' demands to sail for Italy, she does so in front of a plain black proscenium drop curtain which felt more like an excuse for a scene change. Balletic choreography tired and the chorus shuffled on and off stage in purposeless order.

There were beautifully staged moments, none more so than during Dido and Aenaes' stirring Act IV duet, “Nuit d'ivresse/O night of rapture”. Under a sensually lit sky with the city's model raised to resemble a heavenly body, Dido's commitment to her people appeared truly diverted as Graham and Hymel melted together in glorious harmony while Graham's vibrant middle range and elegant top notes dripped over Hymel's thick, warm and resonant tone.

Berlioz never saw the first two acts performed in his lifetime. Act 3–5 were performed as Les Troyens à Carthage in 1863 and the first complete performance wasn't until 1890, 21 years after his death. This production very well carries the spectacle of a grand opera that Berlioz aimed for, but it could have achieved so much more in cementing it as the masterpiece he had hoped to bring to the stage as his lifelong ambition.