Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE market ( Number_cities INTEGER, Market_ID VARCHAR )
TABLE: CREATE TABLE film_market_estimation ( Market_ID VARCHAR, Low_Estimate INTEGER )

### Question ###
What is the average number of cities of markets with low film market estimate bigger than 10000?

### Accurate SQL ###

SELECT AVG(T2.Number_cities) FROM film_market_estimation AS T1 JOIN market AS T2 ON T1.Market_ID = T2.Market_ID WHERE T1.Low_Estimate > 10000