Mark Twain Plaza Office Suites available in Mark Twain Plaza. This plaza offers a campus-like environment and is within walking distance to Main Street restaurant and retailers. Adjacent to Madison County Courthouse with direct access off Vandalia St. and Main St. Mark Twain Plaza I: 3rd Floor – Suite 305 – 2,981 SF Mark Twain Plaza II: 2nd Floor -Suite 212 -1,095 SF for Lease 2nd Floor – Suite 250 – 7,266 SF for Sub-Lease (Rate Negotiable) Mark Twain Plaza III: 4th Floor – Suite 475B – 1,531 SF for Lease