historic district; historic center
Refers to a designated area of a town or city preserved for its historical character, often with old buildings and streetscapes.
Many old buildings remain in this town's historic district.
Tourists enjoy strolling through the historic center.
旧市街 often refers to the old town or old quarter of a city, while 歴史地区 is a more formal term for a designated historic preservation area.
Compound of 歴史 (history) and 地区 (district, area).