Simultaneously one of the most intimidating and rewarding destinations in all of the Mediterranean, Athens is one place where it really pays for tourists to do a little advance research (particularly if your visit is going to be a brief one). Wander into the City of the Violet Crown (or City of Angry Greeks, as it is known by others) without plotting your course ahead of time, and you’re likely to end up overheated, worn out, ticked off, and light in the wallet. Happily, the number of opportunities for rewarding sightseeing and exposure to history, culture, and entertainment is staggeringly numerous.
If you have just one day, the main thing to do is limit the number of major tourist attractions that you plan to try and visit. Obviously the Acropolis, the Ancient Agora, and the Temple of Zeus, etc. beckon to many, and they are absolutely worth visiting, but you’ll need much more than one day to do them justice. Many of the most alluring sites in Athens can be taken in at a distance from the top of the top of Lycavittos Hill, which can be reached on foot (approximately a 30-minute trip), or via funicular railway from the top of Ploutarchou Street in Kolonaki. If you want to go in depth, you should pick just one major attraction and spend the rest of the time enjoying the modern city.
If you want to try and cram as much in as possible you can take this Half-Day Sightseeing Tour which includes the Acropolis and other ancient sights, or get a Hop-on Hop-off bus pass to create your own route around the main attractions. Another way to take in the city in a hurry is by bike. Every Saturday and Sunday, a free bike tour departs from Thissio Metro Station at 10:40 a.m. A variety of professional tour groups also offer cycle tours of the city and surrounding area throughout the week for a fee.