Grand Hotel is an option, though you may also stay wherever you’d like! Grand, Puro, and B&B are some recommendations with good location, and there’s a wide array of options for different styles and price points. For visitors unfamiliar with Łódź, I’d recommend staying at most 3km or so from Piotrkowska Street/City Centre so you can walk to and from City Centre as you please, though you can also get around town easily and quickly via public transit.