Don't even think about a rental car. When traveling Europe, underground train lines, called metros, can take you almost anywhere throughout the city. All of the subways in Europe have their quirks, and each city has a unique system. Once you get the hang of it you'll be able to see just about everything a city has to offer—without spending a fortune on cabs.
When you get to your destination, grab a map at your hotel or a visitor's center, and mark everywhere you want to go. Many of the bigger cities' metro systems have their own smartphone apps that will help you get around, like the London Tube, Paris Metro, Berlin U-Bahn, and Barcelona subway.
You can also download more general apps like Metro Europe, MetrO, and Spotted by Locals, and choose your city from there. If you want to see some of the city above ground, most subway tickets can be used for buses.
In the U.S., the interstate is always packed during rush hour. And if you live in a city with trains, you already know that it's the same with most subways. If you get on right around 5 p.m., it will be standing room only with zero personal space.
You can usually buy tickets at the stations, newsstands, or tobacco shops. Before buying 20 single-ride tickets, you should check out the available deals for single-day or week passes. Also, in many sightseeing cities, you can purchase a card that gives discounted or free museum entrance and unlimited metro access for a specified period.
London: The Tube
The London Underground, known as the Tube, opened in 1863 as one of the first stations in the world. It now has 250 miles of track and 270 stations. If you plan to visit London, be prepared to take the Tube.
Because unless you have a month to toil around the city or a good internal compass, taking the Tube is the best way to get to Buckingham Palace and the Globe quickly and with little confusion.
The lines generally start by 6 a.m. (7 a.m. on Sundays) and stop right around 11:30 p.m.—midnight. But be aware, because different lines have different start and end times. You can save money by purchasing a pay-as-you-go Oyster card or a Travelcard, which gives you unlimited travel within certain zones.
If navigation just isn't your strong suit, you can download the London Tube app for just $0.99. The app will give you step-by-step instructions and travel times to get you to your desired destination with little thought required on your part.
Rome: The Metropolitano
Opened in 1955, Rome's metro was the first in Italy. With a total 26 miles of track, it is one of the smaller systems worldwide. It consists of two lines that cross each other at the central Termini station. Also, a few commuter lines connect to the metro at different locations, allowing public transit access to the suburbs.
Don't be put off if you see any performers or musicians in the metro stations, in Rome or elsewhere. It's normal. But do be aware that stopping to listen or watch obligates you to tip them. Walking past is not a problem, but standing there for a minute, then giving them nothing is impolite.
The metro runs from 5:30 a.m. to 11:30 p.m. every day except Saturday when it runs until 12:30 a.m. The Rome metro is fairly cheap, with a single ticket for 1 euro and a week pass for 16 euros. If you plan to see the city, forget the moped you've seen in movies and head to the metro. There is an app available for metro travel in Rome; however, you should find that Rome's metro is one of Europe's simpler systems.
Warsaw: Metro warszawskie
One of the newest metro systems, Warsaw's 13.5 miles of track and 23 stations opened between 1995 and 2008. The metro, which runs along the Vistula River, is still under construction, with another 4 miles to open sometime in 2014.
This metro is known for elaborate station designs and a commitment to sustainable technology. Its trains are the most up-to-date. If you're interested in sustainability and green city planning, check out the University of Warsaw library, which has one of the world's largest green roofs. You can get to it from the Politechnika Metro station.
The metro runs from 5 a.m. to 1 a.m. every day except Friday and Saturday when it keeps going until 3 a.m. Other commuter lines connect Warsaw to the rest of Poland, but the ticket prices differ. Definitely invest in a good metro map, as the systems are still changing and therefore there is no reliable app currently available.
Paris: The Métro
The Métro opened during the World Fair on July 19, 1900, to an underwhelming amount of fanfare. However, now the 133 miles of track, 300 stations, and handful of beautifully designed stations make it a prominent part of French culture.
Métro tickets also work for the lift at Sacré-Coeur. In case you don't want to climb the 300 steps up to the basilica, you can use one ticket to go up. Although Notre Dame de Paris is the most famous cathedral in the city, Sacré-Coeur provides the best view of the whole city.
The rails are open Sunday to Thursday from 5:30 a.m. to 1:15 a.m., and Friday and Saturday from 5:30 a.m. to 2:15 a.m. Single-ride tickets are 1.80 euro, but if you buy a pack of 10, it saves money. The price goes up if you're trying to go to Versailles or destinations outside the city, because you have to connect with an RER commuter line.
The Métro is actually one of the world's safest subways when it comes to violent crimes. However, the city is known to have a notable pick-pocketing problem, so be sure to keep your eyes on your purse. When it comes to beggars, do like the French: don't make eye contact.
Also, one last note: While eating on the run is a common way of life in America, it is NOT in Paris. Save the snacking for the cafe, unless you want to get a few dirty looks when your pain au chocolat stinks up the entire train car.