Until recently, the classic old bicycle would have been an obvious option for anyone wanting to get active outdoors. These days, however, there are a number of electric alternatives that require slightly less exertion. But e-bikes and e-scooters aren't always as eco-friendly as you might think, and can cause other problems too.

The e-bike, an enhanced bicycle if you will, is probably the best-known electric alternative to regular bikes. The battery motor makes it move faster and is especially helpful on inclines. One problem: Because it makes biking less exhausting, more seniors who would normally not head out into the traffic anymore, ride e-bikes. That has lead to an increase in accidents.

Another issue with e-bikes is the battery, the production of which requires a lot of natural resources. E-bikes run on rechargeable lithium batteries. Digging this metal out of the earth is no easy feat and requires large lithium mines. It's also a finite resource. In 2018, the world's remaining lithium reserves were estimated at 53.8 million tons.

Electric modes of transportation don't emit CO2, but e-bike batteries have to be charged regularly. The same is true, of course, for batteries of e-scooters, e-skateboards monowheels, hoverboards, … See a trend there? The demand for electricity is growing and not all of it is met with energy from renewable sources.

As companies keep coming up with cool new e-gadgets for us to buy, the number of batteries that need to be charged is likely to keep rising. In addition to regular e-bikes, there are even e-unicycles. Not into peddling? Then how about a hoverboard, inspired by cult classic "Back to the Future II"?

E-scooters are similar to the scooters you might remember from your childhood. These new ones, however, don't rely exclusively on our feet to propel them forward, but on battery power. That makes them more eco-friendly than vehicles with a combustion engine, but many people only use them to travel the "last mile" from a bus stop or car park to wherever they're going.

Up until now, zipping along the streets on an e-scooter was illegal in Germany. Because of their little "engine," you'd need certain permits for e-scooters (like a license for a car), but those weren't available. Starting in the summer of 2019, Germans will be allowed to drive e-scooters with a maximum speed of up to 20 kph (12 mph) on bike paths. In the US, that's been legal for a while.

Denmark's capital boasts a 350-kilometer (217-mile) cycle path network, traffic lights that prioritize cyclists, and footrests on the roadside when you have to wait for a green light. No wonder, then, that 63 percent of the population cycle to work. The word "copenhagenize" has already become established in English to describe making cities more bicycle-friendly.

Amsterdam in the Netherlands is one of the most bicycle-friendly cities in Europe. Cyclists in Amsterdam cover some 2 million kilometers (approx. 1.24 million miles) a day. The country is popular with cyclists because it's very flat. Utrecht, for example, is home to the largest bicycle parking garage with 33,000 parking spaces.

In Paris, the city authorities have been systematically expanding the cycle network for years. On Sundays, entire streets are even closed to traffic. As a tourist, one can also easily mingle with the cyclists, as there are bicycle rental stations everywhere. This is also the case in Strasbourg. The two cities count as the most bicycle-friendly in France.

Malmo in Sweden has invested a lot of money in improving its bicycle infrastructure. There are almost 500 kilometers (311 miles) of cycle paths with (tire) pumping stations and right-of-way systems. Probably the most creative idea is a bicycle hotel with its own workshop, rental bikes — and bike parking directly in front of the rooms.

Trondheim in Norway is a hilly city. The "Trampe", the world's first bicycle lift, provides a solution. The 130-meter-long (426 ft) lift takes up to 300 cyclists per hour up the mountain to the Kristiansten Fortress. A plate, on which you can stand with your right foot, is pulled along a rail. This plate then pushes the cyclist together with the bike up the hill.

In Münster in Westphalia, there are more bicycles than residents. It is therefore not surprising that Münster is the city, after Leipzig, with the highest bicycle theft rate in Germany. But that doesn't stop people from riding their bikes — after all, Münster offers wide cycle paths, plenty of parking spaces and no hills.

As early as 2002 you could ride a rental bike through Barcelona. 250 kilometers (98 miles) of cycle paths connect destinations in the Catalan capital. Zones limiting speeds to 30 kmph ensure more safety in city traffic. For tourists, the city offers various themed cycle paths through the city, to the beach or to the sights of architect Antoni Gaudi.

In Basel the land is flat and the distances short. The streets are particularly crowded during the slowUp. During this event, which takes place in summer in different cities in Switzerland, the organizers block off around 30 kilometers (18.6 miles) in beautiful surroundings for cyclists and provide them with a wide range of activities along the route. What could be more fun?