One usually finds that land in recognized centers, such as hotel, club, theatre and amusement, shopping, manufacturing centers, etc., has a peculiar value. Then it is necessary to know the requirements for proper improvements, such as the capacity of a building necessary to create a paying investment, the amount of land needed, the proportion which can be built upon, the cost of construction, the income desired, and the transit facilities. The center of population, which, in a growing city, is constantly changing, must be carefully watched to appreciate when it is time for a shifting of these centers for the convenience of the citizens. Comparatively young men have seen the theatre centers change from below Astor Place to Union Square, next to Herald Square, then Times Square, and now from Columbus Circle to Lincoln Square, with 125th Street and Seventh Avenue and 149th Street and Third Avenue as additional centers. So also have the hotels and clubs moved northward, as they naturally continue to follow the residential portion of the city.