Act as a professional graphic designer with 10+ years of experience in minimalist branding. Create a sleek, modern logo for a [luxury real estate agency] specializing in [urban high-rise properties]. The logo should embody elegance, trust, and sophistication while maintaining extreme simplicity. Use a monochromatic color scheme with optional [gold or silver accents] for a premium feel. Focus on clean typography (sans-serif) and subtle geometric shapes like buildings, keys, or abstract skyline silhouettes. Avoid clichés like roofs or houses—aim for a timeless, upscale aesthetic that appeals to affluent buyers. The final design should work equally well on business cards, billboards, and digital platforms. Provide 3 distinct concepts with variations in layout and negative space usage.