City Level is the level of the players' city in Bloons Monkey City. The player can level up when they get a certain amount of Experience. The highest city level on flash is 40. Players can gain various amounts of XP by doing any of the following:
Capturing new tiles, which in flash, may also be done by successfully defending an MvM attack. MvM attacks in flash will target the lowest value tile adjacent to the city (which, perhaps with similarity to bloons beacon, may avoid tiles with specific rewards so as to avoid Special Missions; Treasure Chests Volcanoes and Caves). Captures by MvM defense will result in an XP reward relative to the level of the attack. A player that has evenly pushed out borders: while buying a minimum of towers, while buying upgrades for a minimal range of towers used and while not fulfilling unnecessary quests, will receive a relatively low XP reward from defending MvM attacks. A player that has left relatively low-value tiles unconquered while expanding their city along spoke-like paths; while getting several high-value upgrades, and while pursuing all available quests, will receive a relatively low XP reward from defending MvM attacks.
The advantages of gaining higher levels include:
Greater access to buildings, towers, upgrades and decorations. Some upgrades and buildings require a certain City Level (similar to rank in other BTD games) before being bought. Once the player gains enough XP, their city levels up.