First, you'll need to add a field in your Data Extension that has a static value (e.g. LookupKey, with a default value of 1). You can only do a lookup with an equals operator. Then you'll need to set it for your existing rows -- probably easiest with an export and overwrite import.
Once that's done, then you can use that LookupKey value in your lookup...something like this:
%%[
var @i, @cities, @row, @rowCount, @maxRows
var @City, @prevCity, @Area, @Salon, @Number
set @maxRows = 0 /* up to 2000 */
set @cities = LookupOrderedRows("Cities" ,@maxRows, "Number asc", "lookupKey","1")
set @rowCount = RowCount(@cities)
set @prevCity = ""
for @i = 1 to @rowCount do
set @row = Row(@cities,@i)
set @City = Field(@row, "City")
set @Area = Field(@row, "Area")
set @Salon = Field(@row, "Salon")
set @Number = Field(@row, "Number")
if @rowCount == 1 then
write(concat("<ul>"))
endif
if empty(@prevCity) or @City != @prevCity then
set @prevCity = @City
write(concat("<li>",@City,"</li>"))
endif
if @rowCount == @rowCount then
write(concat("</ul>"))
endif
next @i
]%%
Reference