|colspan="2"|City upgrades are special buildings found in the Extensions tab of any house info window. The bonus received will apply to all Different extensions get unlocked as you progress through the houses standing in eras of the catchment area game. There are three main types of each such extension town upgrades: [[City Upgrades#Public|'''regardless<span style="color:#0a0">Public Services</span>''' of which house]], [[City Upgrades#Relax|'s Extensions tab the building was chosen from. '''Warning<span style="color:#00f">Relax</span>''' There is distance limit on building ANY of the city extensions. You may build it no more than 4 squares from the the closest city building. In other words, you can have 4 empty squares ]] and the building must be placed on 5th square from the closest building. Buildings bigger than 1x1 have ONE square of their footprint assigned as the [[City Upgrades#Luxury|'''<span style="Maincolor:#408" one. That square is the one which must be at the 5th square from the town>Luxury</span>''']], you might have to rotate the building to be able to place it on desired locationand two special: [[City Upgrades#Constr|'''Constructions''']] and [[City Upgrades#Pollution|'''Pollution Zone''']].

Different extensions get unlocked as you progress through the eras of the game. There are three main types of town upgrades: [[City Upgrades#Public|Houses in these '''<span style="color:#0a0">Public Servicesgreen</span>''']], [[City Upgrades#Relax|'''<span style="color:#00f">Relaxblue</span>''']] and [[City Upgrades#Luxury|'''<span style="color:#408">Luxurypurple</span>''']]catchment zones will automatically upgrade to generate more passengers, growing the city. It does not matter which specific extension of each color you build - whether you want to build only Wells, or a varied selection of Wells, Markets and two special: [[Saloons is up to you. You might find the latter approach more decorative, but the former works just as well. City Upgrades#Constr|'''Constructions''']] extensions must be built with at most 4 empty squares separating it from the nearest city building, or you get the "Must be built within a city" error message. This means that larger stations (stations with many tracks) can make it impossible for the city to grow to "the other side of the tracks". If you start off with a smaller station (no more than four tracks wide), and only expand it once the city has grown to either side, you will be able to place extensions on the other side and [[City Upgrades#Pollution|'''Pollution Zone''']]make your city grow around your cities. Buildings bigger than 1x1 have ONE square of their footprint assigned as the "Main" one. That square is the one which must be at the 5th square from the existing town; you might have to rotate the building to be able to place it on desired location.