Asgard Mythical Travel Poster

Create a vertical vintage travel poster for destination_name, subtitle subtitle_text. Show a majestic mythical Norse citadel in a frozen mountain valley, centered symmetrically across a reflective lake. A cracked stone causeway leads from the foreground toward a glowing arched gate in the palace. The palace is tall, dark navy and ivory with sharp spires, gold-lit windows, purple hanging banners, carved geometric ornaments, and four visible black wolf statues on tower rooftops. Add snow-capped mountains on both sides, small surrounding fortress buildings, floating ice and rocks in the water, and rune-like standing stones flanking the foreground path. Across the sky, place one enormous diagonal rainbow bridge/Bifrost arc sweeping from lower left to upper right, with exactly four broad bands: purple outer band, deep blue band, pale white band, and golden yellow band. The sky should glow with northern lights in teal, turquoise, violet, and deep indigo, with vertical aurora shafts and a few tiny star glints. Use a stylized Art Deco travel-poster illustration style with flat geometric shapes, crisp silhouettes, layered depth, painterly texture, high contrast, and a cool palette of indigo, teal, lavender, snow white, and muted gold. At the bottom, include a dark navy title block containing a small centered line of promotional copy reading promotional_copy, then the huge spaced uppercase destination title, and beneath it the smaller spaced uppercase subtitle with a thin gold divider line and small diamond ornament. Keep the composition centered and cinematic, no photorealism, no people, no modern objects, no watermark.