Why, you ask?
Well travel photography is a challenging proposition because your desire to travel light, move frequently and reduce the amount of lens changing that will be necessary bumps up against the wide variety of things you will encounter to photograph.
Think about it for a moment; you will need to focus in close on details (a macro lens), you will encounter tall things or tight quarters (a very wide angle lens) and you will see distant things that you want to bring close (long telephoto lens). Wow - that's a problem. You will need to photograph in many different light conditions (a fast lens). What is the minimum I really need?
When I use my Canon equipment here is my travel gear:
1) Camera body and Canon 15 - 85mm zoom.
2) 24mm f2.8 lens
3) 50mm f1.8 lens
4) 70-300mm lens
The 15 - 85mm zoom does much of the work. It is wide enough most of the time and gives me some telephoto for portraits and scenics.
Both the 24 and the 50 are fast and great for unusual light conditions. The 50mm is for hand held night photos.
The 70 - 300mm tele zoom works well for most things. If I am traveling to photograph birds, I bring a 400mm lens.
When I travel with my Sony equipment here is my travel gear:
1) Camera body and 16 - 105mm zoom lens
2) 50mm f1.7 lens
3) 55 - 300mm zoom lens
4) 35mm f2.8 macro lens
If you are trying to figure out what lenses you need, here's my suggestions.
Most interchangeable lens cameras come with an 18 - 55mm zoom lens. It is usually one of the cheaper lenses the company makes. But it is a fine lens to start with. Later, after you have gained more experience, you may want to find a lens with a little wider range. A 16mm or 17mm gives you more wide angle and a 70 or 80mm provides just a bit more telephoto.
The next lens that will provide the most usefulness, is a telephoto zoom. Either a 70 - 200mm or a 70 - 300mm zoom is a nice addition and you will use it a lot.
Then you might want to add a 35, 40, or 50 mm lens with a larger opening (aperture) for darker days, rain, storms, late evening or night. A f1.8 or f2.8 lens will let more light in, will allow you to narrow your depth of field to emphasize an object or put the background out of focus. It will also permit faster shutter speeds when you need them.
If you enjoy photographing tiny details, a macro lens can be a great deal of fun.
Travel light but carry enough equipment to meet your photographic needs and interests. It is a big mistake to carry too much equipment!