Copenhagen's new CityCirkel electric buses emit less CO2 than cars or ordinary buses, and their route (Route 11) is ideal for leisure and business travellers visiting the city:

Albeit it isn’t an actual sightseeing bus, it runs past top tourist sites such as the City Hall Square, Tivoli and the Round Tower, making an entire loop in about an hour. CityCirkel buses run all day long (they return to the garage to be recharged at night); tickets are the same as those used for traditional buses, trains and the Metro.