ST. LOUIS — New York City-based Nassimi Realty has acquired Millennium Center, a 20-story office tower located at 515 Olive St. in St. Louis. The building comprises 260,000 square feet of space, including ground-floor retail. The center is occupied by tenants including law firms Evans & Dixon and McAnany, Van Cleave and Phillips. Nassimi plans to upgrade and reposition the building to attract additional tenants. The building was acquired from Los Angeles-based JNF Development for an undisclosed price.