Bucharest Palace of Parliament (the world's second largest building with 3,100 rooms, an iconic landmark of the communist era, the Historic center with Stvropoleos church and Lipscani district for cafés and bars, Museum of Romanian Peasant, Romanian Athenaeum for classical music enthusiasts, Triumphal Arch.
Casa Ceausescu, the private villa of the former leader with an extravagant indoor pool (only guided tour), the National History Museum with the Gold Treasure, Cotroceni Palace is amazing (self guided tours), Museum of Art Collections, and National Museum of Art. Sighisoara UNESCO medieval citadel, clock tower and a 12th century Transylvania-Saxon town, the birthplace of Vlad Dracula, the Casa is now a restaurant with the same name. Sibiu's old walled city with three interlocking squares, the fine Brukenthal museum, the Evangelical church with the country's largest organ with 6002 pipes, the church tower can be climbed, ASTRA National museum complex. Tulcea the hub for boat trips to the Danube Delta UNESCO.Suceava for its nearby Bucovina Monasteries UNESCO (Dragomirna, Voronet, Humor, Moldovita, Sucevita, Bogdana). Sinaia Peles castle. The amazing wooden churches of Maramures UNESCO in Budesti, Surdesti, Desesti, Ieud. Sapanta's unique and colorful Merry Cemetary. Villages with Fortified Churches, Biertan, Valea Viilor or Viscri UNESCO. Sighetu Marmatiej Sighet Prison, now a museum. Cluj Napoca Mathias Rex monument and square with cathedral, Botanical garden, Turda underground Salt mines, a true gem. Alba Julia with Carolina castle, and roman ruins on the hill. Rosie Montana Gold mines UNESCO (for guided tours min. 5 people), Sarmizegetusa Regia Dacian ancient culture ruins, best by car, road is fine now, last stretch uphill walk just over 1 kilometer, UNESCO. Horez Monastery, beautiful frescoes, UNESCO. Brasov, Black Church and town square, stayed in Bella Muzica. Strada Sforii, narrowest street. In Targu Jiu is the Central Park with a few monuments created by the famous Romanian sculptor Constantin Brâncuši, now a UNESCO site.
Timișoara has some excellent squares with historical buildings plus the Orthodox Cathedral.