East End

Ostend (German pronunciation: [ˈɔstʔɛnt]) is a quarter of Frankfurt am Main, Germany. It is part of the Ortsbezirk Innenstadt IV. The name means "East End". wikipedia

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Frankfurt’s Ostend ("East End") developed to the east of the city ramparts on ground used as gardens and fields. As of the mid–19th century, a residential area emerged here for members of the middle class working in trading, small businesses, and handcrafts.

When the Frankfurt ghetto was liberated around 1800, a large part of the Jewish population chose to move to the East End. Many families settled close to existing religious and social institutions, kosher shops, and Jewish neighbors. From 1850 on, the Jewish Community and the newly-founded IRG began to have new buildings constructed. Around 1895, almost a quarter of the population of the East End was Jewish.

https://www.juedischesmuseum.de/en/visit/detail/jewish-eastend-frankfurt

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The Frankfurt Zoological Garden, the East Harbor, the former Großmarkthalle and the Frankfurt School of Finance & Management are some of the well-known institutions in the Ostend. The European Central Bank has also built their new seat close to the Großmarkthalle at the Main river. The Hoch Conservatory are also located in the Ostend. (wikipedia)

The area seems to go as far north as the Jewish cemetery where R Hirsch's kever is located and as far south as the Main river. Seems to me that the area is roughly 1 km by 1 km. From the Friedberger Anlange where the new IRG shul was located to the Zoo where the Realschule was  located is about 200 meters. From the Zoo to the Main is 400 meters. The whole city is 95 square miles. Boston and San Francisco are 50 square miles. NYC is 300 square miles. Chicago is 220 square miles. 

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 Israelite Religious Society (IRG)

by the end of the 19th century there were two separate Jewish communities in Frankfurt, the main community (also known as the Israelite community) and the small separatist group, known as the Israelitische Religionsgesellschaft (Israelite Religious Association, or IRG). The IRG was strictly orthodox and had its own synagogue from 1907 at the Friedberger Anlage

https://metahubfrankfurt.de/en/jmf/stories/community-schism-in-the-19th-century

Friedberger Anlage

Friedberg facility

You can get a tour of the East End

 https://www.juedischesmuseum.de/en/visit/detail/jewish-eastend-frankfurt