Four51 Marlborough introduces a contemporary residential building into the fabric of Boston’s Back Bay neighborhood. The project reinforces the character and texture of historic Marlborough Street through its use of brick, precast limestone, and black steel windows, materials found throughout the Back Bay. The massing of Four51 builds from a lower scale of the adjacent townhouses up to a taller corner element, transitioning to the height of the neighboring Charlesgate building, formerly a landmark Boston hotel. The street facade is punctuated by individual townhouse entries and window bays, that continue the intimately scaled residential character of the block, and a graciously scaled main entry, framed in cast stone and granite. Here, a lobby with a concierge area provides elevator access to residential units and to underground parking. Most units have outdoor spaces including rear gardens, terraces, and a penthouse roof deck with commanding views of the city skyline.