What a lovely housewarming gift! The modern look of the condo makes me want to suggest a shiny and highly glazed pot perhaps in a deep red or black color to match the railing. You can make a dramatic statement with an evergreen yew like the tall and narrow \"Hick's Yew\" and this tidy shrub will survive heat and cold in a large pot. You will than have room around the base of the shrub to add pansies and bulbs in the spring and summer annuals like lobelia spilling from the edge of the pot. White lobelia would be lovely against a black pot don't you think? Of course you could substitute a tall and narrow arborvitae or a juniper like the 'sky rocket' juniper or even the Hollywood juniper. Have fun deciding and Keep Growing, Marianne Binetti