Friend: Hey, welcome back from London! How was your trip?

You: It was great, thanks! London is such a cool city.

Friend: I bet! Did you get to ride the Underground?

You: Oh yeah, I used it a lot. It's so convenient and easy to get around the city.

Friend: That's awesome. How does it compare to our subway system here?

You: Well, the Underground is a lot older and much bigger. There are 11 different lines and they cover pretty much the entire city.

Friend: Wow, that's impressive. Were the trains crowded?

You: Yeah, especially during rush hour. But I found that if you avoid peak times, it's not too bad.

Friend: Good to know. Did you have any trouble figuring out which line to take?

You: Not really, they have signs and maps everywhere to help you navigate. Plus, the locals are really friendly and willing to give you directions if you need it.

Friend: Sounds like a great transportation system. I'll have to visit London one day and check it out myself.

You: You definitely should, it's a must-see!