Short answers, pulled from the story.
The earliest physical evidence of synagogues is a stone-carved dedication inscription from the second half of the third century BCE. This artifact emerged in Lower Egypt and marks the beginning of known synagogue history.
The Old Synagogue in Erfurt, Germany dates to circa 1100 and stands as the oldest intact synagogue building in Europe. Parts of this structure are now used as a museum of local Jewish history.
Samaritan synagogues typically face Mount Gerizim while Jewish synagogues orient toward Jerusalem and the Temple Mount. Samaritans strictly avoid depictions of man or beast due to commandments against graven images.
Large Jewish communities constructed magnificent synagogues across Western Europe and the United States using Neoclassical, Renaissance Revival, Neo-Byzantine, Romanesque Revival, Moorish Revival, Gothic Revival, and Greek Revival styles. Most historicist synagogues did not attempt a pure style but are best described as eclectic.
The Paradesi Synagogue in Kochi, Kerala, India was built in 1568 by the Paradesi community. It remains the oldest active synagogue in the Commonwealth of Nations.